Used 3x — until my puppy outgrew. Have the medium now. Airy and light with 360-degree ventilation, the Pet Carrier has a back pocket sleeve to securely place over your carry-on, and a memory foam mattress for elevated comfort. A foldable design makes it easy to pack within a suitcase when not in use. Airline-compliant for cabin use. Poly-mesh / performance-nylon exterior. Size small. - Weight: 4.0 lbs (Small) - Dimensions Small: 15" L x 10" W x 8.5" H - Max pet weight supported: 15 lbs (Small) - Volume: 25L (Small) - 360 degree ventilation ensures a cool and breathable space - Memory foam mattress (removable and washable) - Dual exits and leak proof - Fits underneath the airline seat on medium and large planes