The stock Steam Deck thumb stick grips are honestly terrible, flat with no texture or material grip made my thumb slip while using it. This was the first thing I noticed when using the Steam Deck for the first time and knew that a thumb stick cap was needed.
There was a couple other brands I looked at, but this was exactly what I was looking for - simple design, depth for thumb placement, perimeter raised dots for added grip, grippy rubber design.
The only note is for actually installing the caps over the Steam Deck joysticks. Its a very tight fit - which is great and means there is zero looseness once installed. Follow the noted instructions on the product page and take your time folding it over the edges.