Extra NecksGen helmet-mount kits lets teammates share one NecksGen without sharing helmets. Free shipping when selected via the pulldown menu during your NecksGen REV purchase; cheap shipping everytime else. Comes in a separate box from your REV shipment and includes easy installation instructions.NOTE: Each SFI 38.1 Head and Neck Restraint System has their own proprietary anchoring hardware. Regardless of brand (Z-Tech, NecksGen etc.) please ensure you choose the correct corresponding hardware.