12.5mm OD x 1.5mm x 9.5mm ID is a standard size, it is just a standard metric size. Readily available from a number of industrial suppliers (McMaster-Carr for instance).
G3 bolts are finished and will be on their way to me tomorrow.
Tolerances - I will be measuring the dimensions to verify that they fall within the tolerance range specified. When you design something, the drawings typically indicate a tolerance range, which is effectively how far measurements can deviate from the ideal dimension and still be acceptable. I need to ensure that the dimensions that they are machined to are within the tolerances that I specified on the drawings - too far a deviation and pieces can potentially not fit together properly.
ive been holding out on the he bolt so i can give this bolt a try first. i dont see a need to upgrade my current techt bolt since it works fine.
If you haven't done it look at my thread (http://www.pbnation.com/showthread.php?t=3816088) to mod your Techt bolt. There is no effective difference between the mod and what Techt sells as the HE bolt. Shortening the bolt tail does lower OP and make the gun a little more efficient. I've had a bunch of people send me their bolt head to modify.