150 series is a non insulated suit with an Aluminized outer shell and a flame retardant cotton lining. The 550 series is the same but with a vapor barrier lining of flame retardant neoprene coated FR poly-cotton. Designed for short duration ambient heat of 200
Designed for short duration ambient heat of 200F (93C), radiant heat of up to 2000F (1093C).