Onyx - prostate massager by Sinclair Intimacy Institute&re - review by SexyPenis


Prostate massager by Sinclair Intimacy Institute

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Beautiful Black Glass for Front or Back!

With a strong curve, this glass dildo is great for reaching men's prostates or women's G-spots. The flowery etching is subtle and artistic, offsetting the black sheen of the toy without slowing a smooth insertion. This is pretty close to what I think of as an ideal glass toy, with only minimal suggestions for improvement. In fact, just thinking about the Onyx, I think I need another "test run..."
Elegant, safe, smooth, good for newbies
Ridges can be uncomfortable, could be tapered to stay in place better, upper price range for glass
Rating by reviewer:
extremely useful review


Technically, this is marketed as a prostate massager. It's meant to stimulate the prostate internally through the anus. However, since it's glass, it can be sterilized by bleaching with 10% bleach or boiling, and used vaginally or shared. This would also be great for G-spot play vaginally because of the curve. Glass is good for temperature play, either warming up or cooling down in hot or cold water.

The reasonable size makes the Onyx great for solo or partner play, and glass has less drag and requires less lube compared to plastic or silicone and is compatible with all types of lube, so you can have fun in the water or anywhere!

Be sure to take it easy when thrusting as glass is very, very firm and will not bend or compress. Also note the ridges on the underside of the "finger" when thrusting, be careful to avoid discomfort and tearing as these could be uncomfortable over time on the sphincters.
  • Who / How / What
    [ ? ]
    Who might this product be best for? How is it best used? What are the best circumstances or situations for using this product?
    • Couples
    • Solo
    • Temperature play
  • Where
    [ ? ]
    Where / what types of places can this product be used?
    • Anywhere
    • Tub/shower/pool
  • Features
    [ ? ]
    What kind of features does this product offer?
    • Travel friendly
  • Body / part areas
    [ ? ]
    What areas on the body can this product be used / what areas does it stimulate best?
    • Anal
    • G-spot
    • P-spot

Material / Texture

Now I know why people love glass so much. The Onyx is borosilicate glass, which merits a 10 out of 10 for safety, it is shatter resistant, nonporous, and phthalate free. Everything is smooth except the etching, which can't be felt, and the ridges on the "finger," which definitely can be felt on anal insertion and removal, or during extended thrusting. The glass is compatible with all types of lubricant, and even requires less because the glass is so smooth.
    • Not porous at all
    • Rigid
    • Smooth

Design / Shape / Size

The Onyx looks kind of like a stylized, slightly curved finger with ridges on the underside of the knuckle on one end, and a series of three bulbs on the other end. The three bulbs can be used as a joystick handle when inserted, which makes for easy control, solo or for a partner. I think the ridges are meant to contact the prostate but I did not notice them against the prostate, only on insertion and removal. There is a light etching of flowers that wraps around the whole toy.

According to Eden, the Length is 8 1/2 inches, but because of the curve, it doesn't really seem that long.
I measured an insertable length of about 3 inches on the "finger" end. The diameter is a reasonable maximum of 1 1/4 inches on the largest bulbs, but the diameter at the ridges is only about 7/8 inch, which makes for very easy insertion, event though the end is rounded and not tapered. The only tapering is between the bulbs, the "finger" portion is the same diameter, with a little extra where there are ridges. Below is a picture comparing to two Aneros massagers, which do feature stong tapering for the sphincters.

    • Beginner
    • Partner play
    • Whimsical / artistic


This was extremely easy to use. The firm glass provided comfortable massage and milking of the prostate. The handle would probably not work with a harness and does not feature a suction cup. Because there is no taper on the "finger" end and the glass is so smooth, the Onyx was very likely to slide out unless gripped firmly, but the handle is very ergonomic and easy to control.
    • Comfortable
    • Easy to use

Care and Maintenance

Borosilicate glass is super easy to care for, just don't scratch it! Simple soap and water is fine for normal cleaning, but it can be sterilized for sharing between openings or partners by using a 10% bleach solution or boiling. The Onyx is even dishwasher safe, although I personally wouldn't want anything used anally in my dishwasher.

No worries about any type of lube, glass is compatible with everything!

I've been keeping it in the molded plastic that it came in, as no pouch was included.
    • Easy to clean
    • Easy to store


The toy arrived in molded plastic with a cardboard covering.

All packaging
side back view
Other Side

The packaging has no real usage instructions and minimal care instructions, which is understandable because glass is so low maintenance. I did find it interesting that just below the UPC it says "SOLD AS A NOVELTY ONLY" and on the side it is listed as a "CLITORIS VIBRATOR" in 6 different languages. Maybe I've been misusing it the whole time? If it's really a vibrator, this is a great innovation!
    • Discreet looking packaging
    • Good for storage

Personal comments

This was my first glass toy and I was really excited to try it out. So far it's lived up to the hype about glass. I really liked the small diameter and smooth glass that doesn't require as much lube or preparation, but I really didn't like the ridges, maybe I will get used to them over time. They certainly haven't stopped me from using the Onyx, as I've been exploring for three days straight. The only other complaint is that I wish it was a little tapered to help it stay in place without assistance, but I can understand that would risk breaking at that point, so maybe it's for the better. Perhaps someday I'll plunk the money down for the Pure Wand.


This toy can be INTENSE. I had never been able to get much pressure with any of the Aneros or even my finger, but the Onyx delivers. Hopefully with a little practice I can reach the prostate orgasm. In the meantime...wow. The handle makes maneuvering very easy and accessible from a variety of positions, such as reaching behind while laying on a side or stomach, or reaching in front between the legs while laying on the back, or kneeling or squatting, allowing for penile stimulation as well, which is a dynamite combination.
Follow-up commentary
As far as I can tell, this is a slight redesign of the Select Crystal G by the Sinclair Institute. Based on the measurements given by Eden, the Onyx is slightly longer, but I think this is incorrect; I think they are basically the same size from reading the descriptive review on the Select Crystal G and the manufacturer's website. I am not a fan of the redesign, as the major differences appear to be the ribs and the slightly more rounded end. I agree with a reviewer on another site that these are not improvements. I've used it a few times since writing the review but overall, it does not seem to reach the prostate all that well, at least for me. I finally tried inserting the bulbed end but this was very uncomfortable.

It's still fun, easy to insert and clean, only requires light lube, and all the other wonderful things about glass, but I just can't say I'm going to use this that much. Maybe I'll get a longer glass toy at some point, I do love the fact that it's glass but this one just doesn't quite thrill me.
This product was provided free of charge to the reviewer. This review is in compliance with the FTC guidelines.
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This review was edited by
  • ImaGodiva ImaGodiva
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  • SydneyScreams
    Welcome to the world of glass. Hope you'll stay a while

    Thank you for the review!
  • Rossie
    Thank you for the useful review. The Onyx really does resemble a finger!
  • Hallmar82
    Thanks, great review.
  • dancingduo
    Wow. I have been looking for the next thing...matbe! Thanks!
  • Ningyo
    Excellent review. I might get this when it's stocked...
  • Beautiful-Disaster
    Thanks for your review.
  • SexyRob
    Thank you for your review~!
  • SexyPenis
    Thank you for all the great comments!
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