... weight,and compact structure.2.2Air cooling structure,pressure rise 98Kpa,no need of water cooling.2 ... reliable running with low noise under the high pressure condition.2.4Precision harden-teeth-surface helical timing ... with filter,outler silencer,pully,belts,belts cover,pressure release valve, check valve,flexible joint,pressu-re ... more,feel free to ask me. oxygen making use high pressure roots blowers