The Gul Petrel 7 Seas Cap features Revofit 3D molded technology, to create the optimum fit and comfort cap, that gives outstanding hydrodynamic performance. The Petrel 7 Seas cap uses 96g + silicone which is double the weight of the average 2D 48g swimming cap, that helps to reduce heat loss from your head so you can stay comfortable in the water for longer. Key features > easy to use, comfy and streamlined to deliver you ultimate performance. > 100% 3D silicone > Glow colour option features Firefly Technology which allows the cap to glow in low light conditions and is a great safety feature for open water swimming. > can be worn under the Gul neoprene skull cap for additional warmth.