Best reusable gel flasks

Agree on either Hammer or First Endurance flasks. The GU ones are too big and the cap is a pia IMO. I wanted them to work but they seem to work their way out of the jersey pocket and the flex make them clumsy to work on the fly. I take a hammer type flask and use industrial velcro to have it on the stem to grab quickly. GU used to make a holder to put on the top tube or stem but not sure if they still do. Flasks make it so much easier and far less messy.