I typically have to bag with a 21 due to the amount of growth on a number of my lawns. It's not bad though. The bag only fills up once per lawn in most situations, so I'm not having to stop to empty it numerous times at each property. On the flip side, this could easily avoided if I ran a bigger mower that actually mulched properly, but my boss never has ponied up the money for that type of upgrade. At this point, I'm not too concerned about getting that upgrade since I'm planning to switch careers after this Fall.