This is a Titanium replacement bolt for the chrome plated steel seat binding bolt that threads into itself used on most road racing framesets and the occasional mountain bike frame. The steel ones generally have a rectangular "key" that seats in the frame to hold the nut piece of the binder set . This keydoesn't appear on the SRP because it's an entirely machined bolt, not cast. The SRP bolt is turned on a lathe, drilled and threaded. Instead of the rectangular "key", the SRP bolt has a 6mm allen fitting on the "nut" side and a 5mm allen recess on the bolt side, so common wrenches are used against each other to tighten the bolt assembly. The SRP Titanium seat binder bolt weighs 5 grams, complete. It will close to as narrow as 18mm, or open and fasten as wide as 25mm. $ Price in Catalog
Machined from Titanium 6Al-4V rod, there are two models of this bolt, a standard size and an Extra Long. These bolts have smooth aero styled conical ends with allen fittings. All the quick release type of seat bolts add many extra grams to the weight of a bike. If you don't really need the quick release feature and want to save weight, you could use this seat binding bolt. It is made to tighten the seatpost into one fixed height, prohibiting quick adjustment while riding. The bolt has a 5mm allen head fitting. The nut has a 6mm allen head fitting, so commonly on hand bicycle tools will handle installation simply. The largest distance the standard bolt will close on is 31mm, the smallest distance it will close on is 10mm, and weighs 10 grams. The largest distance the Extra Long bolt will close on is 37mm, the smallest distance it will close on is 15mm, and weighs 11.5 grams.