Gottlieb and Williams have used 3/8-16 x 2-3/8" acorn 5/8" head leg bolts
for many years, while Bally and Data East used the same basic size, but with
the smaller acorn 9/16" head instead. All manufacturers use the same basic
head bolt size, which has a 9/16" head. So if you end up with a bunch of
legs bolts of different head sizes you now know that the smaller size are
One advantage with the Bally leg bolts is that they match the head size of
the head bolts, meaning you only need a 9/16" wrench to disassemble/assemble
I believe Bally went to the larger leg bolt head size in the late 1980s.