Bolt grips can be bought individually or as a set in a number of sizes, in either metric or imperial measurements.
Bolt grip size (Fraction)
Millimetre
Bolt grip size (Fraction)
Millimetre
5/16
8
11/16
17
3/8
10
3/4
19
7/16
11
13/16
21
1/2
13
7/8
22
9/16
14
15/16
24
5/8
16
1
25
Bolts are measured according to their nominal diameter, which is the width of the smooth portion under the bolt head. A set of bolts may all have a nominal thread size of M6, but come with a number of different lengths and head sizes. Below are the bolt dimensions available: