FERNIDA Heated Pants USB Electric Thermal Heating Trousers Cold-Proof Bottom Men/Women(Battery Not Included) XS

Why isn't there a large size? Looking for my son who is 6'4"and very slim with size 32 waist & 36" length inseam in jeans. What size would he need

How many hours keep warm after charge and is waterproof? Thanks

5'5 110lbs which size do I get? Xs or s

Do you sell replacement heating pads