fia0001 's Japan Review

Since Cosmo's O-rings are thinner than those made by other companies, we were concerned that when using conversion tips made by other companies, the rubber would stick out depending on the barrel, making it impossible to tighten them securely.

When I changed to this O-ring, it did not stick out and I was able to tighten the O-ring beautifully. It's very handy to have one of these!
In my case, when I used Target's titanium tip, the ring no longer protrudes and the compatibility is much better.

I felt the effect on parts that did not fit well and parts that tended to loosen even after tightening.
I never felt that the durability was weak even though it was thin.

Also, when removing the O-ring, a toothpick can be used to remove it cleanly.

O-ring arrived today. Installation was surprisingly easy. I threw it immediately, and it does not loosen between the barrel and the shaft at all even though I threw it quite a bit. I feel like a fool because of the stress caused by the loosening.... I wish I had bought this product earlier.
The o-ring almost came out when I tightened it, but if I put the o-ring to the end of the thread (open one thread), I was able to install it beautifully without the o-ring coming out (I am using a special shaft for fit flight).

When I used O-rings from other companies, I had to stop using them because I was worried about them sticking out.
This product does not protrude at all and does not loosen the shaft, so I am very satisfied with it.
Since O-rings themselves are not something that should be replaced so often (for me), I think the price and the amount of contents are also sufficient.

I use it between DMC Sidewinder SUS and RX converter (normal).
It is a great product without any complaints, having all three features: no sticking out, no gap, and no loosening!

If you have a barrel and shaft that don't match and tend to be loose... I recommend this.
It eliminates the stress of having to close it every time.

The ring I had been using was sticking out a bit. I bought it based on the other reviews and I'm so happy I did! It doesn't stick out at all, which is good!

Best of all, it's thin! I think this is the thinnest O-ring.
If you don't like the lumpy feeling when you tighten the shaft, this is a good choice.

Cosmo Darts O-rings are recommended because the rubber is thinner than other manufacturers, so the O-rings do not stick out from the joint between the shaft and barrel or the conversion and barrel.

This is the first time I have purchased O-rings. I am very satisfied with the results. I use it between the barrel and the shaft, and it is the first time that the shaft does not come loose. Until now, I had to repeat the process of loosening the shaft while throwing and then fixing it. However, after using this ring, I no longer have to do that, and it has clearly reduced my stress. I highly recommend this ring because it allows me to concentrate only on throwing.

Unlike other O-rings
I like it because it doesn't stick out from the shaft like other O-rings!