6061 Aluminum quick release seat clamp
Sizes 28.6mm, 29.8mm, 31.8mm or 34.9mm

-28.6mm clamp fits 25.4mm post/28.6mm = 27.8mm - 28.8mm diameter seat tubes

-29.8mm clamp fits 27.2mm seat post/31.8mm = 29.0mm - 30.1mm diameter seat tubes-Steel frames 

-31.8mm clamp fits 27.2mm seat post/31.8mm = 30.2mm - 32.1mm diameter seat tubes-Aluminum frames

-34.9mm clamp fits 31.6-31.8mm/33.5mm - 35.2mm diameter seat tubes