Hobbyweld 15 (83% Argon, 15% Carbon Dioxide, 2% Oxygen) As Hobbyweld 15 has been given the name ‘universal’ gas by customers, this shows that the gas can be used for many applications. This gas mix contains a higher CO2 content than the Hobbyweld 5 so offers combined benefits of good welding performance and minimal spatter make it very popular among the agricultural, on-site and mobile welding market. This gas is used in structural steel work and general fabrication. Hobbyweld 15 is recommended for use with mild steel at a thickness of over 7mm. For thinner materials, please look at Hobbyweld 15