These are Du-Bro's "Permanent Mount" 8-32 Blind Nuts.

Features

Zinc plated, metal construction.
Ideal for mounting engines, landing gear, cowls, hatches, etc.
The perfect mounting nut for hard to reach areas.

Includes

(4) Blind Nuts

Requires

Drilling a 5.5mm hole to install

Specifications

Diameter: 12.7mm OD of flange
Length: 7.5mm
Thread Size: 8-32