M-Parts 2 Pairs of Self-Adjusting 12-1/4" X 3-3/8" (12.25" X 3.375") Electric Trailer Drum Brake Assemblies Kit for 9,000/10,000 Lbs (9K/10K) Trailer Axles; 2 Left Hand + 2 Right Hand; 4 Included Self-adjusting brakes automatically adjust to deliver optimum performance and braking power 7 Bolt Mounting Flange Pattern; Easy to Install; Dust Shield; Dexter Axle Replacement Parts, Compatible with most trailer axle manufacturers. Total Units Included: 4 M-Parts 12-1/4 x 3-3/8 Inch Drum Fits 15 inch 16 Inch Wheel 16-1/2 Inch Wheel 17 Inch Wheel 17-1/2 Inch Wheel