[R1234YF Low Side] Blue is R1234YF low side quick connect, low side R1234YF plug is 14mm female x 1/4" SAE male. Adapter from R12 to R134a: 1/4" SAE female x 13mm R134A low side quick connect. [Easy to remove and install] The R134A to R1234YF quick coupling has an auto-off function, making it easier to remove and install.