Mountain Buggy 12" INNER TUBE
When you get this product you might (like I did) think it doesn't fit your Mountain Buggy and is too big but it actually does. Put it in the tyre before transferring both tyre and deflated tube to the wheel rim then inflate and you will see it is designed in a certain way that it will fit.
I can't fault the company, arrived very quickly. The product must also be quite robust because in my efforts to make it fit I knocked it about loads and it did not puncture!