Just signed up and was pleased to have found your web site. Especially the PE90/550/551/552 stuff. I am having my 556/551 upper refinished and can't wait for it to be back home. Bought a 551 parts kit from MarCoMar and it has been over four months since I sent if off. The pictures here help a lot. I had them make me a 551 and 552 flash hider because I liked them both. Barrel is cut down to 13" and registered as an SBR.