This was the closest size available to fit on my Kowa TSN-550 Prominar. The strip of felt that is double sided taped to the inside of the ring made the fit too tight. Once I removed the felt, it was too loose. I took a similar piece of felt out of a larger ring (also outdoorsmans) and it was much thinner. After purchasing and applying my own double sided tape and using the felt from the other outdoorsmans ring, I was able to achieve a workable, but certainly still not a perfect fit. I suggest measuring the OD of the eyepiece for any rings that are purchased, and do not rely on the size chart provided on the product page (this is how I ended up with an extra ring to steel felt from). Rings will cover 1 of 2 camera lenses on Iphone X. This is problematic if you wish to use the zoom feature while digiscoping.