I bought a new Kubota W5021 about 15 years ago, best walk behind mower ever built! Still works like new, never given me a lick of trouble. The turbo fan really assists in throwing the grass which in turn packs it in tighter to fit more in the bag. The curved handle makes it the most ergonomically comfortable mower.
So far this thing is bullet proof, but I did recently buy extra blades, air filters and another bag just in case Kubota stops stocking parts for it.
I still have the full color brochure from when I bought it, I'll try to scan it and post it. The W series came in two sizes the W5019 (19") or the W5021 (21"), and you could get it with or without the blade clutch and with or without self propelled. Mine has self propelled and the blade clutch. The "residential" version is what I have and it's better built and engineered than other commercial mowers, Kubota also had the "commercial version which had steel wheels that were also taller than the plastic residential model. The commercial model also had a larger fuel tank and the catcher bag was black instead of white.
It's a shame that Kubota never sold enough of these to warrant a continued production of them, not only are they build tough they also look good (if a mower can look good).
