Nimbus Double Bolt Clamp
Clamp is made to fit 22.2mm seat posts.
Clamp’s actual internal size is 25.4mm.
Alloy clamps with two steel bolts for extra clamping power! power! power!
A 22.2mm seat post uses a 25.4mm clamp.
A 25.4mm seat post uses a 28.6mm clamp.
A 27.2mm seat post uses a 31.8mm clamp.
Some Eclipse and Equinox frames need a 34.9mm clamp
These are a rule of thumb. Yet, variety exists.