Libra New 12-1/4" x 3-3/8" Trailer Electric Brake Assembly pair for 9K-10K lbs axle - 21008 New OE 12-1/4" x 3-3/8" electric trailer brake assemblies (1 left + 1 right) for 9k-10K lbs axle works with 9K - 10K GD lbs trailer axles. Center Hole Diameter: 4-7/16", casted back plate 7 holes mounting, bolt circle diameter: 5.5", Replace Dexter style 10K brakes