Thin - Hard Formula - approximately the same viscosity as 30 wt. motor oil. It is easy to apply a thin, shellac-like clear coat that will cure in seconds when irradiated with sunlight or our UV flashlight. This product is a very durable aliphatic urethane which characteristically does not yellow with age.Thick - Hard Formula - Get back on the fish! Work with it as long as you need to as it will only cure when exposed to UV light. It is also great for repairing damaged flies or repairing home projects in a flash!