ButtonHex socket head cap screw(Ansco(JIS(Coarse Stainless steel Unplated 8 X 25 Pitch 1.25

JIS B 1174
A hex socket button head cap screw characterized by its rounded head profile.
Also known as a button cap screw.
Compared to a hex socket head cap screw of the same size, the hex socket is smaller.
There are two types of button cap screws: the "3S Standard," an industry association standard (union standard) that was established first, and the "JIS Standard," which was later established in accordance with ISO. The two types differ in head dimensions.
3S Standard (Manufacturers: Tokosha Metal SS, Goshō SS, Chubu Raši, Kyokuto SS, Ansco (Maruko))
JIS Standard (Manufacturers: Nissan Neji, Ansco, Alps Seiko)
Button CAP Standard Comparison

• Button cap bolt Ansco JIS Coarse pitch
• JIS B 1174
• Nominal diameter (d) M8
• Length under head (L) 25.0
• Coarse pitch 1.25
• Head diameter (dk) Max 14.00 Min 13.57
• Head height (K) Max 4.40 Min 4.10
• Hex socket width across flats (S) Nominal 5 Max 5.140 Min 5.020
• Hex socket depth (t) Min 2.60