Which motor size will fit? | Finished width and thickness both matter [OK Prostate Chip]

This page is based on entries from "ok-lab's diary" (https://ok-lab.hatenablog.com/), the Japanese development diary written by Mr. Okada, founder of OK Lab, a small company in Japan (Okada Comfortable Life Laboratory). Only the entries about "choosing between 6 mm, 8 mm, and 10 mm motors" are summarized here, in order of publication. Past prices and sizes are as written at the time. Current prices come from the official product list (retrieved September 4, 2026). Quotations are translated from Japanese.

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Note: This page is a personal reading log by someone with no connection to the maker or the seller. It reflects the source entries as of their publication dates and makes no guarantee of accuracy or safety. The product is not a medical device; talk to a doctor about any health decision. Check the official site for current information. This page contains advertising.

In short

• Motor diameter alone does not describe the finished chip's width or thickness.
• Mr. Okada's answers weigh dimensions, vibration strength, controller compatibility, and connection strength.
• Current vibrating products remain listed, but the product list does not confirm their motor options.

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About this product

The OK Prostate Chip is a small device that is placed in the urethra (the urine passage) so that it acts on the prostate; the maker sells it in several shapes, sizes and materials. It is made and sold by OK Lab (Okada Comfortable Life Laboratory), a small company in Japan, through its own online store, and prices are in Japanese yen (JPY). The maker's development diary, "ok-lab's diary", is written in Japanese. This page is an English summary of it, and every quotation is translated. OK Lab ships internationally, so readers outside Japan can order (see "Buying from outside Japan" below). Product names on this page are plain-English descriptions. The official Japanese product name is shown once in the product table so you can find the same item in the store.

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Before you read: key terms

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What happens: prostate vibrator size

The OK Prostate Chip is a small device placed in the urethra (the urine passage) to act on the prostate. Its vibrating versions add an electric motor to supply vibration to the chip. That motor sits inside a resin cover (a molded covering for waterproofing and support), often at the chip's rear end. The diary compares motor diameter, finished width, thickness, vibration strength, and the controller (the device supplying and regulating power).

The 8 mm motor suited shorter chips in early prototypes

In an entry published in January 2019, Mr. Okada described a better match between motor size and chip shape. He considered the 10 mm motor suitable for long chips and the 8 mm motor better balanced on semi-long chips. He wrote that smaller motors supplied less vibration energy.

These were early resin prototypes. No matching product can be confirmed on the current list. Mr. Okada also offered custom combinations with the motor sizes reversed.

(Source: ok-lab's diary, published January 2019)
https://ok-lab.hatenablog.com/entry/20190119/1547879323

A 10 mm motor could become too wide after covering

In an entry published in March 2019, a customer asked about altering a vibrating chip whose rear section would not fit. Mr. Okada declined reworking a used chip but offered an 8 mm motor-unit replacement for ¥3,000 (about $19 at ¥156 = $1, rate as of 2026-09-04) excluding tax, as published then. The diary does not record whether that replacement was completed.

Separately, the entry records another customer ordering an 8 mm product after an oversized one would not fit; no use result follows. Mr. Okada cautioned buyers that a 10 mm motor became 11mm–12mm wide under its resin covering.

(Source: ok-lab's diary, published March 2019)
https://ok-lab.hatenablog.com/entry/2019/03/09/150813

The 8 mm motor disappointed Mr. Okada during ceramic testing

In an entry published in June 2019, Mr. Okada tested a ceramic long chip in size M with a motor attached. He reported that the ceramic attachment needed less resin than the glass arrangement while retaining connection strength. This was a test build ahead of the planned ceramic vibrating range.

No matching product can be confirmed on the current list. Mr. Okada cautioned that an 8 mm motor might lack enough power for a long chip.

(Source: ok-lab's diary, published June 2019)
https://ok-lab.hatenablog.com/entry/2019/06/22/123034

An 8 mm motor could fit across but remain too thick

In an entry published in August 2019, a customer said width was acceptable, but thickness prevented the vibrating chip from fitting. Mr. Okada explained that available 10 mm motors could approach 2 mm thick, while his thinnest 8 mm motors were about 4 mm. The resin-covered assembly reached about 6 mm thick.

The customer's returned unit ultimately measured 5 mm thick. The diary does not record how that changed version felt in use. Mr. Okada warned that the thinner covering reduced strength and that he could not guarantee long-term durability.

(Source: ok-lab's diary, published August 2019)
https://ok-lab.hatenablog.com/entry/2019/08/10/125102

The 6 mm motor initially seemed too weak to adopt

In an entry published in October 2021, a customer who could not fit an existing motor requested a smaller component from another supplier. Staff declined attaching a customer-supplied motor without the trials required for a new component. Mr. Okada estimated that a 6 mm, 2.5 mm-thick motor offered less than half the energy of his 8 mm, 3.3 mm-thick motor.

He also judged the 10 mm, 4 mm-thick motor to feel about twice as strong as the 8 mm version. These comparisons were his estimates and impressions. Mr. Okada cautioned that the smaller motor could leave the customer dissatisfied with the vibration.

(Source: ok-lab's diary, published October 2021)
https://ok-lab.hatenablog.com/entry/2021/10/09/125823

An 8 mm motor shipment brought greater thickness and power

In an entry published in March 2022, Mr. Okada reported receiving motors that differed despite being ordered to the previous specification. The new 8 mm motor was about 0.6 mm thicker, and he found its vibration stronger. Existing stock remained the default at that time. Mr. Okada asked buyers wanting the stronger version to identify that preference in their order comments.

(Source: ok-lab's diary, published March 2022)
https://ok-lab.hatenablog.com/entry/2022/03/05/123200

A 6 mm motor's original wiring failed during custom production

In an entry published in June 2024, a customer requested a custom linked-chip vibrating device (Alien) with motors in different sections. Mr. Okada accepted the challenge despite previously saying that such a build was difficult. He reported repeated failures while making it, including factory-attached wires coming loose under slightly stronger force on the 6 mm motors.

The assembly was awaiting drying and further checks. No matching product can be confirmed on the current list. Mr. Okada made delivery conditional on satisfactory checks, including a stronger pull test.

(Source: ok-lab's diary, published June 2024)
https://ok-lab.hatenablog.com/entry/2024/06/22/122918

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The maker's answer to prostate vibrator size

The maker's answers depend on the finished assembly, its controller, and the connection method.

The 6 mm motor required specifically approved controllers during testing

In an entry published in January 2022, Mr. Okada reported a stated operating range of 2.7V–3.3V for the tested motor. He reported burn-level heating at about 5V within 20 seconds. At 2.5V or below, it did not rotate; he also reported damage when power rose again after dropping below its working level.

His trials with several other controllers ended in motor failures. He was still testing before a proposed release with controller restrictions. Mr. Okada limited compatibility to OK Lab's standard electronic controller and its USB-rechargeable electronic controller.

(Source: ok-lab's diary, published January 2022)
https://ok-lab.hatenablog.com/entry/2022/01/22/123342

The thin 8 mm motor offered another way to reduce thickness

In an entry published in July 2022, Mr. Okada announced an 8 mm motor measuring 2 mm thick. He estimated that a covered assembly could be about 4 mm thick. By touch, he judged it stronger than the 6 mm motor but weaker than the standard 8 mm motor. Mr. Okada offered this thinner component for requests from that publication date.

(Source: ok-lab's diary, published July 2022)
https://ok-lab.hatenablog.com/entry/2022/07/23/123014

The 6 mm motor was excluded from flexible-joint builds

In an entry published in February 2026, Mr. Okada introduced a vibrating design with a flexible connection to a ceramic chip. It used nitinol wire (shape-memory wire connecting the parts). He did not offer a 6 mm motor because he doubted the reliability of its wire connection.

No matching product can be confirmed on the current list. Mr. Okada limited that design to 8 mm or 10 mm motors, including thin, standard, and thick versions of the former.

(Source: ok-lab's diary, published February 2026)
https://ok-lab.hatenablog.com/entry/2026/02/14/121602

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How prostate vibrator size changed over time

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OK Prostate Chip products related to prostate vibrator size

The current list includes vibrating chips, but it does not specify their motor-size options.

Products that appear in these entries

The ceramic semi-long vibrating chip is listed in OK Lab's own online store.

The plain motor-only vibrating chip is listed in OK Lab's own online store.

(Source: ok-lab's diary, published December 2019)
https://ok-lab.hatenablog.com/entry/2019/12/28/131319

Products the diary mentioned as alternatives

The diary names no alternative.

No longer sold: In an entry published in February 2020, Mr. Okada discontinued builds leaving any motor metal exposed. He said he lacked assurance that the metal was safe for bodily contact, despite his tests raising no durability or waterproofing concern.

(Source: ok-lab's diary, published February 2020)
https://ok-lab.hatenablog.com/entry/2020/02/22/145216

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Common worries about prostate vibrator size

Readers asked about finished dimensions, motors that stopped, and the trade-off between width and vibration.

"Does an 8 mm motor mean that finished width?"

In an entry published in September 2019, a customer considering a custom three-motor chip asked how motor choices changed its dimensions. The production reply gave maximum covered widths of 10 mm for an 8 mm motor and 12 mm for a 10 mm motor. The customer then requested the smaller-motor configuration, but the entry does not record its performance.

No matching product can be confirmed on the current list. Staff advised leaving out the optional aluminum covering unless specifically wanted, because it added thickness.

(Source: ok-lab's diary, published September 2019)
https://ok-lab.hatenablog.com/entry/2019/09/28/140637

"Could motor size explain why vibration stops?"

In an entry published in April 2022, a customer reported an illuminated controller but no vibration. Staff initially explained that some motors needed a higher starting level. The customer replied that vibration still stopped even at maximum output, particularly between patterns.

Mr. Okada then suspected the motor rather than the controller, without confirming the cause. The diary does not record a repair result. He offered inspection of the returned equipment to establish which part was responsible.

(Source: ok-lab's diary, published April 2022)
https://ok-lab.hatenablog.com/entry/2022/04/02/123050

"Is a 6 mm motor always the thinnest choice?"

In an entry published in December 2024, a customer refining a linked-chip vibrating device request asked whether the chosen motor would fit. Mr. Okada's initial estimates were 10 mm wide and 5–6 mm thick with thin 8 mm motors. With 6 mm motors, he estimated 8 mm width and 6–7 mm thickness.

By January 2025, staff confirmed about 7.5 mm thickness and 8 mm width for the 6 mm assembly with tubing containing wire. Later that month, Mr. Okada called his strength comparisons subjective, acknowledged quality variation, and declined the entire custom request. He suggested standard catalog vibrating products for exploring motor performance instead.

(Source: ok-lab's diary, published December 2024)
https://ok-lab.hatenablog.com/entry/2024/12/28/122907

(Source: ok-lab's diary, published January 2025)
https://ok-lab.hatenablog.com/entry/2025/01/18/123007

(Source: ok-lab's diary, published January 2025)
https://ok-lab.hatenablog.com/entry/2025/01/25/122940

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Buying from outside Japan

OK Lab ships internationally to countries covered by Japan Post's EMS courier service. Overseas orders are paid in advance by PayPal. Each order carries a ¥400 (about $3 at ¥156 = $1, rate as of 2026-09-04) handling fee, and EMS shipping is charged on top. These terms come from OK Lab's official sales-terms page (written here as plain text, not a link: ok-lab.net/docs/law), checked on September 7, 2026; confirm them on the official store before you order, because they can change.

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Summary of this article

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Source: ok-lab's diary (Okada Comfortable Life Laboratory). The original entries are in Japanese; quotations on this page are translated. Photos and videos are on the original entries.