I purchased the 650 series, power propelled electric start, 22". model # 917.376742. works great but the key keeps falling out while mowing. I actually lost it and spent all night looking for it with flashlights not wanting to run over it. couldn't finish mowing until next day after finding the key. Also a key to remember is clean off grass underneath or it will turn moldy.It is not hard to push. The bag does fill up rather quickly. It mulches very well and I did not need the bag if i put in on the highest level of cut. I do have to soak the bag every so often as the holes in the bag get cloggd and the mower won't cut right.