Stainless Steel 5/16-18 Button Head Socket Cap Screws. These take a Hex / Allen key to drive and are made from 18-8 Stainless Steel.

Diameter: 5/16
Thread Pitch: 18 TPI - UNC / Coarse Thread
Type: Button Head Socket Cap Screw
Matching Nut and Washer: 5/16-18 Available here
System of Measurement: Inch
Material: Stainless Steel Grade 18-8 / A2
Specifications: ASME B18.3 / ASTM F879