These are Brass Threaded Inserts from Du-Bro.
FEATURES: Brass threaded inserts. The perfect way to put threads into wood & mount engines to wood mounting rails. Threaded inserts make a simple & effective way to make wing hold downs. These can be used where blind nuts are hard to fit.
INCLUDES: (4) Threaded Inserts
SPECS: Thread Size: 6-32 Length: 7mm