Both trainers are size and shape of the stainless steel Original Quills (standard size)
Blue Quill Trainer is rigid and 3D printed from PRO Series Nylon (procured from MatterHackers). This trainer is printed by G3DPrintables as a solid, rigid structure. The Blue Quill Trainer is best used to practice full impact blows, rakes, and hooks against Body Opponent Bags (or similar) and weapon retention exercises. 
Red Quill Trainer is flexible and 3D printed from Ninjaflex, a specially formulated thermoplastic polyurethane to provide flexibility and longevity. The Red Quill Trainer is printed by G3DPrintables with internal voids at the tips to cushion impact when sparring with a training partner. Ninjaflex material is made in York, Pennsylvania.
Diamond cross section comes to a blunt point.