This flanged button head socket cap screw is made out of stainless steel with a stainless finish The low domed head with a wider bearing surface offer a finished appearance, making them an ideal choice when a neat appearance is desired. This bolt comes with a 0.66" diameter flange head and full thread length of 0.687" with a 3/16 allen hex drive. Thread size is 5/16-18. Used with t-nuts to mount brackets and plates to aluminum extrusions. Quick installation and can be re-purposed over and over. Perfect for your extruded rail projects! Button head screws have a low domed head with a wider bearing surface than standard heads, and they offer a finished appearance, making them an ideal choice when a neat appearance is desired.