A while ago one of my Presta valves failed. The thin inner rod broke. I suspect I have been a little careless in the past with how I put the pump head on (it's the first bike I've had with Presta tubes). I'll try to do better. That was a non removable core, so I had to throw a perfectly good tube away.

Both tyres now have removable cores, so I thought I'd get some spares. I'll probably replace the core on the non new tyre anyway, in case I've damaged that.

But there seems to be a huge difference in price. 4 x Schwalbe cores are something like £14 (UK). Whereas a pack of 12 unknown-make are £7. Is there much difference in quality? I assume they're all the same size. And I don't really need 12.

Thanks.