PelletVent Pro 4″ Type-L Square Horizontal Cap This 4 Inch Type-L Square Horizontal Cap from the PelletVent Pro Series from the PelletVent Pro series is a Type L Biofuel Chimney Pipe component and consists of the duralock system for a tight seal. Use for horizontal terminations only. Cap features swivel collar to adjust exhaust direction. Cap features an optional swivel base. Features: Type: Horizontal Cap. Shape: Square. Material: Galvalume. Use for Horizontal Terminations Only. Swivel Collar to Adjust Exhaust Direction. UL Listed.