A mast cap available in two sizes and offsets for all Trek road bikes with round seat masts. A mast cap available in two sizes and offsets for all Trek road bikes with round seat masts. Trek-compatible seat mast cap Genuine replacement parts Offered in white and black and a variety of lengths and offsets, the mast cap includes hardware compatible with round saddle rails only. 7x10mm carbon rail-compatible hardware sold separately. Trek-compatible seat mast cap. - Ultra-light carbon construction Ultra-light carbon construction - Direct fit on all Trek road bikes with round seat masts Direct fit on all Trek road bikes with round seat masts - Colour-matched for direct compatibility Color matched for direct compatibility - One bolt head design offers easy fore-aft and infinite angle adjustment One bolt head design offers easy fore-aft and infinite angle adjustment - Includes 7 mm round sadd...