Seal up tight with no leaks.It can work all day and stop the drip.Very clear sight glass and has the markings for oil level.The correct oil level. The threads are long and engage well.Will not bother with the rubber seal that comes on it.That's a strong tight,won't blow out the gasket.It can work in a high temperature environment,and the sealing is realized by the peripheral flat gasket.It can provide good sealing performance and prevent oil leakage during use. The glass is opaque from the oil in the compressor during shipping.This sight glass solve the problem well. Functional:If your crafstman compressor level check glass broke.This is a great fit.Firm and wear-resistant,longer life. Versatile use:Widely used in machine tools,air compressors,hydraulic presses,reducer gears and other mechanical equipment. Material:Brass and Glass Color:Brass Quantity:4pieces Thread size:G1/4 inches The level gauge sight glass are made of light material,good toughness,high strength,corrosion resistance,oxidation resistance.Great fit and stopped the leaks.Fits perfectly on my compressor no more leaks.Widely used in machine tools,air compressors,hydraulic presses,reducer gears and other mechanical equipment.