Then why are they now "back ups" if they're still going so strong? Heck, they'll probably last another 20 years if back ups are all they are, just don't expect to put them into 8 hours a day worth of use. Sorry, don't mean anything personal by this, just this thread about equipment from 'box' stores really clangs my bell. To be the same exact model number, you must compare not only the main part number (example AB 420) but also any alpha coding that follows that number. And it won't be on the equipment itself, you'll only find it on the box. This is the only way to distinguish between many/most pieces of equipment that at quick glance appear to be the 'same'. Makers offer lower prices to mass merchandisers on these 'one off' products because they are built cheaper- period. Plastic or hollow bushings instead of bearings, etc. A few cents here, a few cents there, = equals inferior products at retail level. The word is inferior, not bad or worthless, so don't bother with your stories about what a deal the el cheapo is. They are OK for most home owner's I guess, I'll stick with quality, hard demanding workability, and dealer back up thank you. I haven't even mentioned what I think about Echo. . . .