Z3 USA Made Trimmable Flap Discs, Trimming the backing allows for more of the discs to be used for fewer disc changes and better product rates; Easy trimming, simply angle the backing edge against a hard metal to expose more flap material; Easier heavy duty jobs, stiff backing construction paried with a compacted 4 degree flap angle make grinding easier, quieter and with less vibration; Z3 for fast, long lasting grinding, 20% more material than regular Z3 flap discs, ideal for heacy duty applications.