These were my first projects. I TIG welded them because that`s what I knew and I hadn`t learned to braze yet. The bolted together on on my mtb was my first. It hooks to a mount on the seatpost and has a single pair of struts, the idea being to let it pivot when I raised or lowered the saddle. In theory, it should work- in practice I can`t move the seatpost without twisting it a little and the rack won`t let me do that. It`s the only aluminum one I`ve done (just the platform). The stem is kind of funky too because since I didn`t know how to braze the binder clamps on I had to machine away the unwanted metal the best I could.