SaunaLife Model S4 Wood-Fired Hot Tub The SaunaLife SOAK-Series Model S4 represents the very best in wood-burning hot tub quality, efficiency, and luxury. Features Thermo-Spruce materials (lasts up to 2X longer than Cedar) Luxury outdoor wood-burning hot tub Designed for outdoor ergonomic hot tub bathing experiences Arrives fully assembled and no electricity required (eco-friendly) Spacious interior holds over 304 gallons of pure water bathing pleasure Thick dark grey contoured fiberglass lining