Lightweight, easy to use and reliable, Helium King is the UK's best selling Helium Cylinder. Sold: Pack of 4 Each Helium Tank contains 0.25 Cubic metres of Pure Helium and will fill up to: · 30 x 9” latex balloons · 15 x 11” latex balloons · 11 x 12'' latex balloons · 12 x 18” foil balloons Latex balloons are porous and have an average flotation time of around 6-8 hours depending on the size of the balloon and room temperature. Due to this we advise to inflate the balloons 1-2 hours before the party/event. Treating latex balloons with Ultra Hi-Float (available separately), can make them float up to 25 times longer! Float time of a foil balloon: 5+ days.