Brembo M4 Monobloc Radial Caliper vs Brembo GP4-RS Caliper

The GP4-RS is the newer, lighter, MotoGP-derived caliper and the better pick for a rider who brakes hard on track or mixes road and track. The M4 Monobloc is the proven, simpler upgrade for a 108mm radial front end on a Japanese sportbike, and it comes as a two-caliper kit. Both are cast monobloc aluminum with sintered pads included; the GP4-RS adds finned cooling, ribbed pistons and a 10% weight saving over the M4 One-Piece, while the M4 uses larger 34mm pistons against the GP4-RS's 30mm. Owners report strong, precise braking and good fitment from both, and the GP4-RS is the one to step up to if you want the latest Brembo race hardware.

• Choose the M4 Monobloc if you have a 108mm radial mount, want a straightforward bolt-on upgrade for a Japanese sportbike, and prefer the two-caliper kit with the larger 34mm pistons.
• Choose the GP4-RS if you ride track days or brake hard often and want the lighter, finned, MotoGP-derived caliper with ribbed pistons and Z04 pad compatibility.