Hello

It would help if you would give some indication what size, pressure and movement you are dealing with. Large size bellows are normally specials. Small sizes you can find from manufacturer's lists.

Thumb rule for the length tends to be that the pipe designers give too short length. In addition too low spring rate is often specified. General rule is that lower the spring rate longer the bellows must be.

Spring rate can be a real problem to a bellows supplier. Specific manufacturers have possibility to make very soft (low spring rate) bellows. If you happen to select from such supplier and the buying will go to an other manufacturer the supplier can be in trouble. It is better when ever possible to specify higher spring rate.