The HB4 four-bladed cartridge comes standard on the HeadBlade MOTO and ATX models and delivers amazing performance due to its flow through design and seamless blade construction. We've spent over three years creating a unique pivot that lets the HB4 or HB6 blade cartridge to be used on any HeadBlade, including the original HeadBlade Classic! All you have to do is used the supplied adapter that comes in each blade kit. Kit contains one adapter and four blades. HB4 refill blades can be used on the HeadBlade MOTO, ATX, S4 Shark and all past HeadBlade models.