I use a Tumi International Carry on which is H x W x D: 20.0" x 15.75" x 8.5" including handles and wheels

Air Canada carry on specs are:

Maximum size:
9 in x 15.5 in x 21.5 in
Wheels and handles included.

This bag expands. I can confirm that it WILL NOT fit in a CRJ overhead bin - not even close. I have put it under seat in an exit row, which still gives lots of leg room, or in the FA closet when I'm in J. Last week I was travelling and it was <1/3 full so it wasn't overstuffed. In general, unless I'm in J, on an RJ (100/705, doesn't matter) I will check this bag. It easily fits in a E190 (though not the bin right over 12A).