Elliptical locking feature id
A soft metal or nonmetal sleeve, designed to mate with a pin-rivet. it may include an external wrenching facility which breaks off at a perdetermined torque to form a head.
NSN 5960-00-089-5931
NSN 5835-01-485-0210
NSN 5915-01-633-9845
NSN 5985-00-204-0028
NSN 6220-01-361-5182
NSN 6620-01-444-7053
NSN 5996-01-242-5205
NSN 6610-01-248-4339
NSN 5998-00-153-1378
NSN 5895-01-218-5745
NSN 5915-01-081-7102
NSN 5950-01-167-4649