75 Ohm BNC — not a 50 Ohm drop-in
The 112659-75-12: At 75 Ohm it is the standard for video, broadcast, and telecom signal paths — not the 50 Ohm used in RF test equipment or cellular. Dielectric is PTFE, body is nickel-plated brass.
What bolts in — hardware and fit
The kit includes the connector, lockwasher, and nut — three pieces total. The bayonet lock mates fast; no threading, just a quarter-turn. Shield and center contact both terminate by solder.
75 Ohm vs 50 Ohm — the mismatch penalty
The 112659-75-12 is 75 Ohm. A 75 Ohm jack on a 50 Ohm line gives a VSWR of about 1.5 at DC — that is a 4% reflection, which may be acceptable for video but not for precision RF. If the BOM calls for 50 Ohm, the 112553 is the correct pick. If the system is 75 Ohm video or data, this is the part.