This is based off the ClawMate by Struth Gaming

They are intended to give you a better grip of your mouse. Human hands are meant to curl inwards when gripping, when you do this to a mouse, your fingers on the sides have nothing to hold onto which makes for a weaker grip. This is meant to solve that problem.

Here is a video explaining how to attach them to your mouse. All you need is double sided tape and some alcohol wipes.
https://youtu.be/NYixZzSa1Cw?si=4l8Fxqx3uDwFM_3H

This is made of 3D printing material so it isn't as good as the original product which is made of silicone. If you'd like to buy the product go to https://struthgaminggear.com/products/claw-mate