These 4" Axle Tube U bolt plates are made for 2 1/2" width Leaf Springs, if the center locating pin hole is used it will fit a 3 7/8"-4 3/8" axle tube. These U-bolt plates are also a perfect match for our custom spring perches. Like our spring perches these U-Bolt plates offer 2" of total wheelbase adjustment so that your u-bolts will stay perpendicular to the axle tube. They are laser cut form 3/8" plate and are CNC bent to make them incredibly rigid. Our U-bolt plates also offer slotted u-bolt holes so that if you upgrade to larger axles you will not have to purchase new u-bolt plates to help keep upgrade cost down. These are sold in pairs. Like all of our products, they are made in the USA from USA steel.