SX3 Pulley fences look to be just flat rings, but the SX2 have a lip on them, more like a hollow top hat. Could be an SX2 pulley that you have.
SX3
http://www.racing-cars.com/images/Te...exploded_L.pdf
SX2
http://www.racing-cars.com/images/Te...ded_iss2_L.pdf