The Firstlaw Fitness Shock Mount Heavy Punching Bag Hanger is another great way to hang your heavy punching bag. The Shock Mount uses gas shock technology to greatly reduce the noise and vibration created when training. Be sure to use the drop down box and select the weight of your heavy bag. Every Shock Mount uses the same chassis. The only difference is the force of the gas shock. Your Shock Mount will perform best if the correct bag weight is selected. The Shock Mount with 24" Extensions is designed to attach to open floor joists on 12" and 24" (center to center). It can also be mounted through drywall. For 16" joist spacing please see the standard Shock Mount. Firstlaw Fitness created and manufactures 4 different styles of heavy bag mounts that are designed to attach to wooden floor joist. The Wood Beam Mount (provides no vibration absorption) - The Joist Mount (provides good vibration absorption) - The Shock Mount (provides very good vibration absorption) - The Spider Mount (provides the best vibration absorption you can buy). Please contact us if you have questions which mounting system is the right one for your application.