This is a used GEIGERRIG RIG 500 Hydration Pack. It's a 2-liter capacity hydration backpack designed for outdoor activities like hiking and biking. The pack is in excellent condition.

Key features include its bright yellow color, a 2-liter hydration bladder (though its condition should be confirmed), and multiple straps for a secure fit. It's a practical item for anyone needing hydration on the go.