new blades for Champion 1800W garden shredder. Will these fit?

I have sourced some new blades/knives for my Champion Shredder. Mine have 384985 & 8-00 marked on them. The new ones have what looks like the same number but with 6-00. Any help would be appreciated as I have no idea what these two numbers mean.

I thank Richard for his previous answer as to where I might source some new ones. I'll ring them if these are unlikely to fit.