BN-521L1/BN-521L2/BN-521L3/BN-521L4
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| BN-521L1 | BN-521L2 |
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| BN-521L3 | BN-521L4 |
| Part Number | OEM # | Length | Inlet/Outlet | Sensor | Additional Info |
| BN-521L1 | 7S21A0E | 25 3/4" | 2 bolt inlet, 2 bolt outlet | 1 sensor 3 1/4" from body | 12" round body |
| BN-521L2 | 27 1/2" | 2 bolt inlet, 2 bolt outlet | 1 sensor 2 1/2" from body | 12" round body | |
| BN-521L3 | 28 1/2" | 2 bolt inlet, 2 bolt outlet | 1 sensor 2 1/2" from body | 12" body | |
| BN-521L4 | 29 1/2" | 2 bolt inlet, 2 bolt outlet | 1 sensor 3" from body | 12" round body |