I love this big baby... I debated and debated between 45 and 50 (after I purchased the 50 of course) and I am finally settled on 50 (I think) because more space = more slouch = less like a stuffed sausage when stuffed! I also wanted to be able to fit knee high boots inside. She is large enough to sorta wrap around me and not bounce around when walking! Size also great for when you gotta just throw in that extra pair of flip flops in da bag! No way is she going on an airplane though until she has earned her patina in the back of the SUV!