Quick Link.

Can be used for a verity of things for EG

Chains , cable attachments  and  multi gyms

they come in sizes.

3.5MM STAINLESS STEEL 

M4  4MM X 40MM

M5  5MM X 50MM

M5  5MM X 50MM STAINLESS STEEL

M6  6MM X 60MM

M8   8MM X 80MM