Michelin Ultra Heavy Duty Rear Inner Tube 100/110-100-18 100/100-100-18" TR4 Valve 4.00mm Thick Fits Rear 100/100-18", 110/100-18", 120/90-18" and 130/80-18" Tyres.  

Michelin Heavy Duty Rear Inner Tube 110/90-19 110/90-19" TR4 Valve Fits Rear 110/90-19" and 130/70-19" Tyres.  

Michelin Heavy Duty Rear Inner Tube 100/90-19 100/90-19" TR4 Valve Fits Rear 120/80-19" and 100/90-19" Tyres.  

Pirelli Heavy Duty Rear Inner Tube 100/90-19 / 110/90-19 Pirelli inner tubes are a good heavy duty inner tube. Available in a multitude of sizes.

Michelin Heavy Duty Rear Inner Tube 100/110/100-18 100/110/100-18" TR4 Valve Fits Rear 100/100-18", 110/100-18", 120/90-18" and 130/80-18" Tyres.