Specialized solves the problem of which size spare inner tube to carry on rides.


Fitting the right size inner tube used to be so easy. Mountain bikes pretty much all had 26in wheels, so your only real concern was if you had a tube with a Schrader (car type) valve, but your rim was drilled for the thinner presta valve. That would have been a toys out of the pram moment in the good old days. 

Prest valve

Thanks to tubeless rims, presta valves are now ubiquitous on mountain bikes

Then came bigger 29in and 27.5in wheels, and all their associated benefits. Of course, you can always stuff a 29in tube into a 27.5in wheel, or stretch a 27.5in tube into a 29in wheel – we’ve all done it – but it’s not ideal or easy. Especially when you’re stranded on the side of an exposed hill and the rain is horizontal. 

The Specialized Turbo Levo Comp 2023 electric mountain bike

The Specialized Turbo Levo Comp 2023 has MX wheels, so which size inner tube would you carry?

And what if you have a modern MX/mullet bike with a 29in front wheel and 27.5in rear, like most of the best e-bikes – which size inner tube do you carry or stuff into your down tube storage if you’re an analogue rider? A MX/mullet inner tube obviously!…Yes, that’s right, Specialized now makes a dedicated MX/Mullet inner tube. 

Specialized Mullet Tube

Meet the Mountain Mullet inner tube from Specialized. A neat solution to a simple dilemma

This one-size-fits-all approach, splits the difference between 29in and 27.5in to bring you the ‘tweener size. Specialized calls it the Mountain Mullet tube and it will fit 2.3in to 2.6in width tyres on either 27.5in or 29in wheels. Genius, right? It retails for £8 and has a 40mm presta valve. It’s presta only as all modern rims and wheels are designed to be tubeless ready, and the best tubeless valves are presta. Want to convert to tubeless, then check out our guide to the best tubeless sealants.

mountain bike wheels

Here’s how to ditch the tubes (and the punctures) using Stan’s No Tubes conversion kit

Probably the coolest thing about the Mountain Mullet tube is that it should make everyone’s life a little easier. Best of all, if one of your buddies gets a flat, if you’re carrying the Mountain Mullet tube you can bail them out, regardless of the wheel size they are running.