Portex Equine Stomach Tubes. Premium quality stomach tube. Made from special siliconised PVC tubing, it has just the right amount of flexibility; it won’t become rigid in cold weather and will not soften or kink in hot weather. Each tube has a funnel end to make attachment to a drench pump quick and easy. Available in a range of sizes: Foal (9.5mm x 210cm), Small (12.7mm x 270cm), Medium (15.9mm x 270cm) or Large (19.0mm x 300cm). Note measurements are outer diameter of the tubes.