Piston type posts are economical, while the Wedge type posts are clearly ultra-precise. Both accept the toolholders and interchange with Aloris, Dorian, and DTM Tooling A: 3'' B: 4-5/8'' C: 2-3/4'' D: 5/8'' E: 1-5/8'' H: 5-9/16'' R: 7-5/16'' BXA Wedge Type Quick Change Tool Post for Lathe Swing 10''-15'', 250-222 For Lathe Swing 10 - 15'', BXA Quick Change Tool Post (USA STYLE). Both are precision engineered to assure repetitive accuracy Advanced design provides built-in quick tool changing versatility with positive rigidity to meet the most exacting tolerances.