The gas tank has been useful for storing small items (phone, gels, 1/2 banana, keys, lip balm ,map). Zippers easy to operate on the go. Generally stays where you put it. If packed heavily try to to equalise the weight to prevent it slipping to one side and having your thigh brushing it every pedal stroke. I swap it no probs between road, gravel and MTb bikes. The long Velcro tail did annoy me. Cut it to your length or put a rubber band around it to stop it brushing your thighs.