My current battle with an eBay seller is a top end for the Husq chainsaw. Shopped around, found one with compression release for starting (OE didnt have one), and while letting it sit on the shelf for a few months, I got around to working on it. I was stopped cold because the piston is a 2 groove piston, and I got 1 piston ring.
Argh! Emails back and forth with the (probably) non-English speaking seller. Frustrating to say the least. Check your stuff WHEN you get it, and don't let it sit on the project shelf too long.