A Blockley 820x120 dedicated inner tube size, A correctly dimensioned inner tube made from the best inner tube material (butyl), so you are not pumping them up regularly as with normal rubber inner tubes available elsewhere. These Blockley 820x120 tubes also have a nickel plated valve stem as was the feature on all valve stems in period. Nothing is as good or wholesome as what Blockley produces, because this tube is made for one tyre size only, 820x120.  We are end users of these tubes ourselves which is why we ended up making Blockley tubes, for use in the 820x120 Blockley tyres that we also produce. These inner tubes should not to be confused with anything else available!

Blockley produce one inner tube size for each tyre using our own dedicated tooling. The super thick Blockley 820x120 inner tube is sized for the 820x120 Blockley tyre, and this tube is only for this tyre size, as it should be. But the big companies making inner tubes for profit don't understand this. That is why Blockley has also had to produce inner tubes for the tyres it makes, rather than be able to source tubes, because there is nothing available like what we make. Blockley products are the best you can buy, and cost no more (and often less) because we sell direct to the end user, without the added layer of the  Classic tyre Wholesalers needing to add margins to make it worth their while to sell. One final note on the 820x120 tube. There are many tyre sizes that do not have a dedicated tube made for them, so people use an 820x120 tube - these include tyre sizes 765x105, 815x135, 835x135, 31x4 . . . .

These 820x120 Blockley Beaded edge / clincher inner tubes have an "on centre" nickel plated valve stem with a length of 75mm (3").