Very sturdy and well built.  The rollers/wheels work beautifully, no wobbling.  My heavy, rigid plastic carrier, was really hard on my back and it bumped into my leg at every step.  This makes a trip to the vet much more simple.  The cat can see out of the ample, heavy duty mesh and there are little side pockets to hold medications, etc. This cat is about 9 lbs. and sort of on the small side.  A bigger cat will need a larger size.