Also known as whitworth 55° thread form: BSPT: BRITISH STANDARD PIPE TAPER: Thread form as 1722.1, BS 21, ISO 7-1, DIN 3852-2 FORM C (MALE), DIN 3852-2 FORM Z (FEMALE) BSPP: BRITISH STANDARD PIPE PARALLEL: Thread form per as 1722.2, ISO 228 (THREAD TYPE), ISO 1179: BSPO: BRITISH STANDARD PIPE PARALLEL O-RING