The combination screen rolling tool has a 1-5/16" in. x 3/32" in. convex steel roller at one end and a 1-5/16" in. x 3/32" in. concave steel roller at the other. It is designed to be used with vinyl screen spline sizes from .115 in. up to .165 inch. Dont risk tearing or putting a hole in the screen because you dont have the right tool. Using the correct size Screen Rolling Tool makes the installation job easy and stress-free.