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. Being a double ended spanner, they will specifically fit the B nuts of -12AN and -10AN fittings only with other sizes also sold separately. Recommended to also use in conjunction with the Aeroflow Performance adjustable wrenches or vice jaws to install braided hose to fittings. Available in a complete kit with a Pro Spanner roll up bag for protection included or each Pro AN spanner is sold separately as well.