SFDURA-FLEX | Sierra Flame DuraVent Adaptor | From TTRK-ADP to 4" & 6-5/8" DuraVent570440084SKU:DURA-FLEXInventory ID:03610605Select Item:Price: $66.00Quantity: When converting the flex venting to rigid DuraVent, the SFDURA-FLEX adapter is connected to the top of the TTRK-ADP. Then DuraVent 4" x 6 5/8" rigid vent can be used. Reviews Choose your rating12345