I put my Husqvarna 21" (LC221AH) blade on top of my Toro '22"' 21466 blade. Measuring diagonally, the Husqvarna blade is exactly 21". The Toro blade in my mower is 20 15/16".
I'm in the process of dropping another 21466 powerhead onto the Husqvarna, so in a way this will make the conversion...