The 4187HD is a extremely tough ratchet mount made for the harshest of environments. The Standard (male) 1" x 14 thread mount also has a special cable slot which eliminates the need to remove most factory-installed connectors. Mounting dimensions are; Bolt holes: 5/16" dia., 3" x 1½" on center.
Product Accessories for Shakespeare 4187-HD Stainless Steel Heavy Duty Ratchet Mount
Shakespeare Shim Kit for 4186 & 4187 Rachet Mount. Kit includes Four (4) Shims, two (2) with front/back slope and two (2) with side/side slope. Each shim adds a half-notch (5°) tilt.