Shimano Front mech spacers..please explain1

never read the blurb but having difficulty in understanding how one set of spacers can allow fitting to 3 different seat tube thicknesses. can someone please help an old thicko !
thanks
billboy

the two different sets of spacers fit insode the seat tube clamp to thicken (or reduce) the clamp inside diameter. Use no spacers for 34.9, use one set for 31.8 and use both sets for the smallest diameter seat tube

None for 34.9, thin pair for 31.8 and thick pair for 28.6.

& don’t forget the plastic retainers that hold said spacers too.

Can these spacers be fitted to any mech?
Ive a 34.9 LX front mech and my new frame takes a 31.8.
Stuart.