So I went to Lowes today and they had one of the Arnold Viper Commercial Universal Mulching 22" blades. I picked one up. Thing I noticed is, it is flat. Except for the teeth, it is just flat. The old one was kind of an open trapezoid shape, or something. It does mulch better, but it is as bit noisier, (kind of like the noise the string on a string trimmer makes). It is a 3-in-one (mulch, bag, discharge). Is this the correct type of blade for it?
http://www.amazon.com/Arnold-21-Inch-Universal-Mulching-490-100-0031/dp/B000LO4MSQ
http://www.amazon.com/Arnold-21-Inch-Universal-Mulching-490-100-0031/dp/B000LO4MSQ