headset is dimensioned for the outside, quill stem slips into the inside
tube wall thickness, is 1.6mm , in both cases.. half of an 8th is a 16th.
pick up a decent caliper, PRC makes decent measuring machinist tools too.
digital LCD ones have a button .. Inch/MM..
Last edited by fietsbob; 10-13-12 at 12:34 AM.