This is the RDLohrs Universal 250-450 Zero Pitch Tool. This tool mounts on top of the head and locks the blade grips at zero pitch to allow easy adjustment of links. This tool will work for most 250 – 450 size heads with flat topped blade grips and tee. (Inspired by Helifreaks Finless and Mercuriell) Polycarbonate tool won’t scratch your paint. Some heads may require extra washers/screws to mount.