600/700x20/21 TR11 Heavy Duty ON CENTRE VALVE STEM
An "On Centre" valve stem inner tube thick butyl used on split rim wheels on the large 20 and 21" rims. This tube has a metal TR11 valve stem.
A heavy duty robust correctly dimensioned inner tube, which we use in our Blockley 700x20 tyre. If a longer stem is required it is possible to put an extension on the metal valve stem.