Setscrew - Stainless 1/4"-28
Small Stainless Steel setscrew used in many struts to keep strut bearings in place and some rudder ports, this is the NF (National Fine Thread) some use the coarse thread (ASU-0101)
SIZE: 1/4"-28 NF
Allen Wrench size: 1/8"
NOTE: Inset pic shows NC threads on left, NF threads on right