A Blockley tube marked 600/650x19. A superb quality rubber valve stemmed thick butyl inner tube for the 600 and 650 section 19" tyres. A great product.

We use these inner tubes in our Blockley 600x19 tyres (marked "550/600x19").

Remember if you have a tyre marked 550/600 it will be a 600x19, so this tube is suitable. 

For 18" tyres we have a different tubes. Many other brands lump their 18" and 19" tubes for cost saving. This shows why there are so many actual Blockley tube sizes, rather than a few tubes with plenty of sizes written on them as you get from the Classic Tyre specialists.