These are 4x3/4" 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: 3/4" Diameter: 4mm
COMMENTS: This uses a 1/16" size allen wrench