I had a 50 to repair, pulled the piston, something had gotten inside the cylinder and actually bent the front of the piston causing the ring to stick and no compression. I ordered a 46mm cylinder and piston to replace it. Everything I looked at said it would fit the Husq 50. Guess what, got it in and no it wouldn't fit into the crankcase so ended up ordering a 44mm piston kit, got it, wrist pin wouldn't fit in the piston, extremely close tolerance. Took the ring from the kit, installed it on the original piston, after cleaning up the groove to allow the ring to move freely. Put it all back together and it started on the 4th pull and ran great! So now I have a couple of 46mm cylinders with pistons, Not sure what they fit even though when I bought them, they were supposed to fit. Gotta love it!!