Patagonia's sizing makes absolutely no sense. They advertize the current MLC and the MLC Transport 45 at 45L but the Transport is larger in all dimensions.

From Patagonia's site:

MLC® 45L____________2746 cu. in.____20.5x13.5x7____2lb. 15 oz.
Transport MLC 45L___2746 cu. in.____22x16x9________3 lb. 2 oz.


A box of the dimensions of the MLC is 1937.25 cubic inches or 31.75L. This bag was known to have shrunk over the years -- maybe the older bag was 45L, but the new one is widely known to be smaller than advertized.

A box the dimensions of the MLC Transport is 3168 cubic inches or 51.9L.

Of course the bags aren't perfect cuboids and the fabric, straps and compartments take away space, while at the same times the bags stretch out and deform, so the volumes I calculated are just approximations. That said, it does suggest that Patagonia's claim of 45L for both is an error.