Stand-off from outer edge of idler = Stand-off - (Width of idler - 0.472)/2

Example: Stand-off from outer edge of Idler 3/8 x 3
with shoulder adapter SA3827 = 0.27 - (0.64 – 0.472)/2 = 0.19

6203 bearing dimensions:
40 mm (1.575") OD, 12 mm (0.472") thick, 17 mm (0.669") bore.