Swimming pools and spas not of metal; fibreglass pools and spas; parts and accessories for all aforesaid, including non-metallic liners and lining for swimming pools and spas, but excluding drain pipes and gutters; non-metallic plumbing fittings and hardware in this class, excluding drain pipes and gutters; building materials used in construction of swimming pools, none made of metal; artificial rocks and landscaping products in this class; paving and concrete products for swimming pools