Kizer uses 2 sizes of thumb studs (that I know of), and these are small, designed to fit the hole-opening in the smaller knives - which they do - perfectly. Not seeing any dimensions on this site (despite them mentioning "product detail drawings), I bought them to replace the studs on a Towser K & Towser S, and knew from the moment I opened the package that they were smaller than the OEM studs. Regardless, with care , they installed, but there's plenty of room for them to wiggle around if you do not position and tighten them carefully. The studs are absolutely fine, however the lack of dimensional detail and/or model compatibility is not Hopefully they'll stay put,,, If not, I'll use them on some of the smaller Kizers in the collection.