XP/XR series fans are primarily used with high flow situations. This includes drain tile, gravel or where settling has occurred beneath the floor.
These fans are slightly less powerful than the RP series fans, but can be snugged up closer to a wall since they are all 8.5" inches in diameter. This is 1" inch less than the RP145 and RP140. The XR261 has a similar fan curve as the RP260. But at a full 3" inches smaller in diameter they are an attractive alternative for outside installations.