Review on High-Flow Helix Valve Kit with Soft Bite for Full Flow - Easy QMT Quick Connect Mechanism - Dirt Shield for Dust and Pollution Protection by Johnny Snyder

I've used this for a couple of trips with a Walmart Outdoor Products hydration pack. It's a bit pricey for what it is (this valve is almost as expensive as the package I installed it on) but even if left "open" there won't be a drip unless , it is bitten (or bruised). It's also a nice compact 90 degree nozzle that works well with full face helmets. Some 90 degree bite flaps are still quite bulky and don't slide as well between the chin bar and the actual chin.