A Blockley 550/650x18 thick correctly dimensioned butyl inner tube, with rubber valve stem. Blockleys are the best tubes you can buy, as quality aside, they are correctly dimensioned and made from the best material available for inner tubes - butyl. Nothing is this good! Always remeber to use a rim band, which we also produce.

Note that ALL other tubes available elsewhere today are for fitting in too many tyre sizes! And those marked with the 550x18 size are always too big, for use also in 19" tyres, so quality issues aside, best not to fit them, because they are the wrong size! And this is why we produce Blockley tubes, to rectify what has been (and is) going on. At Blockley for the larger rim 19" tyres we produce a different tyre to suit . . .