Stens 705-020 Carburetor Pressure Gauge for
Detects leaks on carburetor in seconds
Hold a 4 cycle carburetor upside down in your hand and pump to 5 psi and see if the gauge holds and does not leak off. If it holds, the needle and seat are working and not leaking off.
Not compatible with greater than 10% ethanol fuel
The other numbers are not needed.
Use the adapter for a 2 cycle carburetor and pump to 5 psi and see if it holds. If it does, the needle is working.