2.2 - 2.4 20 BMX innertube from Cult. Today's tyres are only getting bigger but the tubes have stayed the same thin sizes over time. Smaller thinner tubes work on bigger tyres but thin out when fully inflated causing flat tyres more occasionally. The CULT Rubbers are specifically designed to fit bigger 2.20/2.40 tyres and they don't stretch and thin out like most tubes on the market.