19 Inches

【Heavy Duty】Our inner tube is thicker than other ordinary inner tubes. 【Airtightness】We use butyl rubber with 45% high rubber content.More resistant to aging and high temperature than natural rubber.It has 5 years longevity,which is twice that of ordinary inner tubes.The good air tightness of butyl rubber allows each inflation to be held for 5 to 6 months.Ordinary rubber needs to be re-inflated once every 1 to 2 months.