I've never been into this kind of thing, but I bought some Facon blades and broke two of them trying to get them in my Milord. Not a good sign but one fit in my Merkur and the shave was ok
Derby Premium blade after 1 1/2 uses. It literally just wasn't cutting it. I've never used a blade like that before in my life. I've used Derby Premiums before & liked them so much I purchased 200 of them. Hope this was just a one-off deal.