At $45 a piece, I just replaced all four (model RF42100). I didn't bother with just swapping out the free-wheeling blocks to try to save myself $90, but possibly pay for shipping a second time. The problem with the second set of blocks is that they are either free-wheeling or locked. I tended to leave them on locked and I can see some wear on the sheet.

I was told to set the crossbeam blocks at the highest setting (harder to lock) and adjust the shroud blocks to preference. I'm currently somewhere between light (easier to lock) and medium and probably need to set them higher. Granted, I'm not racing at this time, so I can not tell you if they work too well or not. But my wife is certainly happier.

Jamie