I use these tabs to hold side plates of lexan to the plastic of my printer to cover up holes. They work for 1/4" thick or thicker plastic. I use 5/8" long 1/4-20 screws to hold 1/8" lexan to 1/4" acrylic. the 1/4" screws screw right into these tabs. window tab 2 has a round part .2" thick so it will hold a .25" piece of plastic tightly. Window tab 2 265 has a round part .265" thick so it will be somewhat snug but you can tighten it down all the way.