My husband wanted to buy a new lawnmower and when I asked whats wrong with the one we've got his reply was quite simply "the blades bent" I avoided clouting him for being so daft, ordered this which arrived in a just a couple of days and took just a few minutes to replace. My lawnmower is now as good as new and my purse is a little richer :)
I got this for a Flymo RE320 and it is very good. I think much better than the original Flymo blade as it seems much sturdier and cuts better.
I have no hesitation in recommending this blade.
However there is a need to check the hole size of your RE320 as there appear to be two different versions with differnt hole sizes. This one has a hole size of about a 1/4 of an inch. The first one I got also for a RE320 had a much bigger hole which did not fit. Don't just go by the model number look at the plate attached to the mower for the part number.
8 year old mower, I trashed the original blade after 4 years (I use the mower to 'vacuum' up twigs and other general rubbish as well as mowing the grass) so I got this replacement in 2012. It also lasted 4 years and is a lot cheaper than a Flymo blade but just as good. I also have not changed my bad gardening habits. This new blade I also expect to last as well.