I had a pair of Bullseye derailleur pulleys. I placed them in a Suntour
Cyclone derailleur. I ran them for a week or two. I noticed something was
not right with them. I asked a former Suntour salesperson. He said that
the " Bullseye derailleur pulleys were not designed to fit into Suntour
derailleurs. Suntour had specific design requirements and Bullseye
derailleur pulleys design did not match those of Suntour's. "
Thereafter, I replaced back the Suntour pulleys .