Z-Flex 4 '' x 5 unstained Steel blowhole Pipe -LRB- 2SVEPWCF0405 -RRB-. This direct piece of pipe a silicon gasket and an constitutional gear clamp on the young-bearing end. The phallic end can be to size with a hacksaw. Z-Flex Z-Vent unstained steel pipe is abstract for the Bosch Therm 940ES / Bosch Therm 830ES / Bosch Therm 660EF / Bosch AquaStar 2700ES / Bosch AquaStar 2400ES / Bosch Evolution 500 tankless water heaters as well as the legacy Bosch Pro 715ES / Bosch Pro 635ES / Bosch AquaStar 2400E / Bosch AquaStar 250SX heaters as well as the Bosch AquaStar 240FX, AquaStar 125FX, Takagi TK1, TK2, TKD20, TKJR, TK1S, TM1 tankless water heaters. Z-Flex Z-Vent is AL29-4C and is approved for Category I -LRB- plumb lonesome -RRB-, II, III & IV applications and is designed for use with boilers, great efficiency gas and oil heaters and water heaters where caller fluke gases are ventilated under pressure. Z-Vent a constitutional, secure gasket and locking band connection. No sealant is.