About this item One 10″ x 2.25″ electric and hydraulic brake (left side), fits most 3500lbs – 4000lbs axle; 4-hole mount w/mounting bolt Fits the wheel bolt pattern 4 lug,fits spline size #84 steel drum; center hole diameter: 3″ ; bolt circle diameter: 4″ Replace 023-026-00 77-10-1 replace Dexter Lippert Al-Ko,etc brake assemblies The trailer brakes are NOT self adjusting, unlike most drum brakes on cars and trucks,need to be done when installed and periodically thereafter.If you cannot adjust yourself, please find a professional adjustment JADODE electric and hydraulic trailer brake parts Making it an Ideal Choice for Travelers Seeking a Hassle-Free Power Solution