Finned/heatsink - semi-metallic compound, but on a heatsink. Marked improvement in thermal performance.
 
Compatibility
 
Shimano - most SLX, XT and XTR calipers, assuming clearance for fins.
 
M615, M666, M675, M785, M985, M987, M988, M6000,
M7000, M8000, M9000, M9020, R315, R515, R785, RS785, S700
 
FSA K-Force DB-XC9000, Afterburner DB-XC-9150