testo 312-4 differential pressure gauge Hose set up to 1.2bar for testo 312-4 balloon pump with release screw conical test plug 1/2 conical test plug 3/4 testo fast printer pressure set for gas pressure measurements on heating systems high-pressure plug 3/8 und 3/4 high-pressue plug 1/2 and 1 high-pressure probe 1up to 25 bar system case