The noise canceling is great! During the trip I got 42 mpg but have no other comparable trips to determine the difference the bag made to gas milage. l got this specifically for breastfeeding on chilly fall days and this ones great! So glad I did, felt a little tight at first, I have wide feet, but after wearing them about the house for a few days they are a perfect fit and so comfortable! They are very warm. I was so very pleased when I opened the box and saw such wonderful looking slippers. Had I know the details I would never have purchased the item. The final, and worst issue is moisture retention. THEY FIT VERY WELL. The thing broke off as I was assembling this unit.