Zirconia 3" Blue Cloth Quick Change Disc P024 BX/25 R 3QC-24G-Z-25 Starcke #: R 3QC-24G-Z-25. Premium Blue Zirconia grain on heavy duty cloth backing for sharper cutting power and longer lasting performance. Type R Male Roll-on connection.. Exceptional results in grinding applications in metal, autobody, marine and fiberglass.. Max RPM 20,000.. Professional grade, German quality.. Stocked & shipped from the US. Starcke is family owned with over 100 years of experience in manufacturing abrasives. 3QC-24G-Z-25