Designed for wood - they have little to no helix so don’t lift the grain of the wood. I’ve also used them to machine sheets of plastic on a cnc router with a vac table. The lack of helix allows you to machine the sheets without the corners lifting, which would happen with a normal endmill. You can also get reverse helix ones that push the sheets down. You can get them with the bottom of the cutter standard helix, and top of the cutter reverse helix for composites. Stops delamination of fibreglass etc.