When I purchased my walker a few years back I opted to purchase a pair of wheels with glide caps to make the use of my walker easier for me.
The pair of wheels by Drive Medical Design and Manufacturing that I purchased have a weight capacity of 500 pounds. They are rubberized hard tires, no air is necessary. They have held up well over the years being used both indoors and out on smooth and rough surfaces.
While the wheels themselves have never been a problem the glide caps that fit over the back rubber ends of the walker so that the back legs will glide smoothly without wheels wear very quickly. My caps were really roughed up after the first couple of uses and completely worn out in a matter of months.
I have found that it is common for the glide caps to wear out quite quickly by any manufacturer. In fact, many people actually replace their glide caps on the rear legs of their walkers with tennis balls. They make a slit in the tennis ball and fit them over the legs. I have not tried this method myself but would recommend trying it before investing money on replacement glide caps.