These are 6x1/2" Button Head Sheet Metal Screws by Du-Bro.
FEATURES: Zinc plated metal construction with clear chromate. Non-slip socket drive insert. The large head of the screw acts as a washer. A new design that's great for mounting servos, cowls, landing gear, etc.
INCLUDES: (8) Screws
SPECS: Length: 1/2" Diameter: 6mm
COMMENTS: This uses a 5/64" size allen wrench