QC-H and QC-L are adjustable quick couplers:

QC-H: for High Side, 14mm*1.5 female thread

QC-L: for Low Side, 14mm*1.5 female thread

The two below ones are QC-12H and QC-12L:

QC-12H: for High Side,1/4" SAE male flare thread

QC-12L: for Low Side,1/4" SAE male flare thread