The Eligo Spile is a "smart hydration" system, which uses their dual fluid selector bite valve with it's piggy-backed electrolyte cartridge injector. The system allows you to choose either water or a water and electrolyte mixture from the same bite valve. The Spile consists of a hose with a hydration reservoir compatible quick connector at one end, and their dual bite valve and cartridge on the other. It fits the newer Hydrapak and Camelbak systems, so your not constrained for either brand. The co-founders, Shane Rogers and Brian Holm, hammered out the design over the last couple of years, and it's an interesting and innovative product.