Aluminum construction

97mm long with 3mm lip makes it 100mm in total length

Silver

Allows the use of a 27.2mm seat post to fit larger diameter seat tubes

3 sizes. 

27.2 > 30.4 = 3.2mm thick

27.2 > 30.9 = 3.7mm thick

27.2 > 31.6 = 4.4mm thick