Yes they are, no they aren't,

Depending on which cage you have and which Sierra youve got!! 3door or Saph

They fit fine into the wheel tubs and floors, but the b post part of the cage may protrude forward away from the b post if you are using a Saph cage in a 3 dr, and if it's a 3 dr cage in a Saph then the b post will be further back in the rear door opening!

Hope that makes sense!