PelletVent Pro 3″ Flex Trim Collar This Flex Trim Collar – 3 Inch Inside Diameter from the PelletVent Pro series is a Type L Biofuel Chimney Pipe component and consists of the duralock system for a tight seal. Use to connect PelletVent Pro rigid pipe to a masonry chimney with stainless steel flexible relining. Female end swivels to allow ease of connection. Features: Type: Flex Trim Collar. Collection: PelletVent Pro. Type L Biofuel Chimney Pipe Component. Use to Connect PelletVent Pro Rigid Pipe to a Masonry Chimney. Specifications: Overall Dimensions: 4″ (D) x 8.5″ (H).