Almost all the fasteners on our bikes are 6,8 or 10 mm, disregarding the axles and a few odd others. Post a picture if possible, of the two holes in question and I'll go take a look see for you. IIRC, then maybe this will help, 6mm= .243" or just under a Qtr of an inch, 8mm=.321" close to +5/16ths" and 10mm=.401" or right between 3/8ths and 7/16ths".
