Premium ceramic grain outlasts conventional zirconium in most applications.Specially designed ABS plastic backing can easily be trimmed away to expose more abrasive material.Unique design is ideal for hand rail and fillet weld applications.Contaminant Free (Fe + Cl + S < 0.1%).Type 29., Only the TrimBack?âòÀÞ?â line of flap discs are able to be trimmed to expose more abrasive overhang.Never trim beyond the maximum trim line (more than 1/4") or the ridged edge of the backing TrimBack?âòÀÞ?â plastic backing.Always mount a TrimBack?âòÀÞ?â flap disc on a properly guarded right angle grinder.To properly trim a TrimBack?âòÀÞ?â flap disc, apply the plastic backing to a secured metal workpiece while the grinder is running.TrimBack?âòÀÞ?â Ceramic is also available in a Type 27 Shape.