The Best-Contoured Files Available on the Market Today. The WELZH 8? Diamond File Set includes four abrasive, diamond-coated hand files (Half Round, Round, Flat and Triangle) that are 20 times harder than traditional files and can be used in any direction, cutting faster and smoother for a better finish. Designed to work in all directions. Cuts into welds and hardened surfaces where other files can?t. Smooth action. 12? overall length with 8? blade.