The Aeroflow Pro AN Spanner is perfect for all hose end assemblies and adapter fittings, providing a perfect fit so they won't mark your fittings. They are Slimline enough to get into all corners of tight spacers. All aluminium spanners are hard anodized black and size stamped. These single ended spanners are designed to suit B nuts of AN fittings from -3AN to -20AN. Recommended to also use in conjunction with the Aeroflow Performance adjustable wrenches or vice jaws to install braided hose to fittings. Also available in a complete kit with a Pro Spanner roll up bag for protection.