The coupling's flexibility should not be used for axial adjustability. High performance couplings are supplied with shim sets to accommodate errors in length at installation. Couplings under 6 inches (152 mm) in diameter generally have +.062 inches  (+1.58 mm), while couplings over 6 inches (152 mm) have +0.125inches (+3.2 mm). Shims should be shared equally between ends so the integrity of the flange pilots is maintained.