icon-arrow-left-4 CAPACITY The pre-wet system poly tanks are sold in sets of 25- or 50-gallon pairs. The tanks are cross-connected to maintain equal distribution of the liquid across the driver and passenger sides of the vehicle. STEEL-CASTER™ models: Available in 50 gallon (two 25-gallon tanks) or 100 gallon (two 50-gallon tanks) kits. POLY-CASTER™ models: Available in 50 gallon (two 25-gallon tanks) kits. Note: Additional tank kits are not compatible with a vibrator.