EVICLEAR WRAS Approved 1/2" Clear Tee. Designed to take 1/2" Pipe - which has an outside diameter of 21.4mm.
Imperial Clear PVC Tee
Please note that clear PVC pipe has a slight blueish / greyish hue and so should not be expected to be 100% optically clear. Clear pipe and it's fittings are often used for sight glasses, process inspection and demo or prototyping units. Other clear Tee fittings are available up to 8".