When your gel flasks become disgustingly encrusted with dried gel and mold, just replace them with these new quality flasks and don't worry about cleaning them.
As you can see in the picture, the flask is curved at the top, so that the push-pull cap doesn't rub against the body when it is being worn on a gel belt. This was a complaint of many users of such belts in the past. These bottles are made of semi-transparent flexible low-density PE plastic.
The caps are US-standard-sized and can be used as replacements for many of the common gel and water flasks on the market (diameter of 33mm (1.3") measured on the outside of the threads). This flask will fit the belts and carriers sold by many other brands, like Ultimate Directions, Lava belt, TNi and Fuelbelt, which use a similar 4oz (140ml) flask. These flasks are brand new and seal 100% with no air/water leakage through the seal.