Exhaust blowers are used for venting the heat out of your grow room. They pull air in the side of the blower and pump it out the front. They have a flange on the front for mounting on a wall or inside a grow box. Some of the exhaust blowers have a round inlet flange for connecting duct tubing so you can pull air off a grow light or from another room.
We also have in-line fans. These are also used for venting heat out of the growing area but they're designed a bit different. In-line fans have round duct connectors on each side so you can use them in-line with duct tubing. They also have mounting brackets to hole the fan in place.
The in-line fans are different from exhaust blowers in the way they move air. Exhaust blowers have a round squirrel cage that rotates. The in-line fans look more like a jet engine on the inside. In-line fans create much more pressure than exhaust blowers and this is very important when you are trying to move air down a tube. An exhaust blower with the same cubic feet per minute (CFM) rating as an in-line fan will not push, or pull air as far down a tube as the in-line.
We also have a few duct boosters. They look similar to the in-line fans but are not designed the same. The duct boosters have an open blade fan on the inside and do not create as much pressure as an in-line fan or an exhaust blower.