The main one is a 4" pipe, slightly squeezed into an oval shape and welded onto a flange. It is perfect for normal guitar sides, as the varying geometry is useful for the different sections of a guitar side. It is heated with a charcoal starter, and I use it all the time for waist touch-ups, bindings, headstock back veneers, mandolins, one-off guitar shapes, you name it.

This smaller one I use for cutaways and tight bends on mando sides and such. It is heated with a propane torch, and it's walls are on the thin side, so it gets quite hot fast, and it is possible to scorch wood if you are not careful. I'm used to it though, so its not really a big problem.
