Clack WS1 Injector Assemblies Part Number V3010-1A Black
Refer to the chart below if you are not sure, noting that most valves are set up as "Down Flow", but some are made to operate as "Up Flow" and this effects which color to select.
Tank Diameter - How To Measure and Why It Matters
"Click"on Chart below for more details and larger version of the Chart
IF you want just the o-rings, then order our AP27F = V3170 and 3412638 = V3171