600/700x21 Race Valved Inner Tube
Tube size 600/700x21 with nickel plated metal valve stem. A good thickness correctly dimensioned butyl inner tube produced by Blockley on tooling specially made for the job (as all other tubes in our large Blockley range). You cannot buy a better product than this.
The metal stem has some advantages over a rubber stem as outlined in our article on valve stems on this site.