Goplus 3HP Air Compressor Aluminum Head Pump Motor 145PSI 11.5CFM Single Stage Twin Cylinder Sturdy StructureThe heavy aluminum structure insures the product long-term durability. Oil Viewing WindowBy observing the oil viewing window, it can monitor the oil capacity inside the machine in real time, and control the amount of oil when you adding the air compressor oil. Smooth OperationThe proven belt driven design is great for excellent compression & smooth running. Keep Cooling EffectIts effective splash lubrication system will keep the pump running cool all the time. Easy to OperateYou just need to unscrew the yellow lid, and then add #100 air compressor oil to the machine.