To replace all of them you will need to order a quantity of 3.

Brass compression nut and sleeve for 3/8" OD tubes.

There are several different air compressor cooling fan styles. Choose this if yours looks like this one. Replace if cracked or missing fins.

Universal Regulator: 4-port, two 1/4" FPT ports, and two 1/8" FPT ports (gauges sold separately here). The regulator controls the amount of air in your air compressor hose. Replace this if you're not able to adjust the PSI to your hose or if it leaks...

Old Part Numbers: SRV187150, SRV187-1/8Air compressor safety valve, 150 PSI, 1/8" male NPT. If your valve leaks below the pressure listed on the side of the valve, replace this vital safety feature.