4 Sets included Adjustable Spacing Allows the ceiling rails to support the bins vertically or horizontally. 2" opening allows for a variety of storage bins bins to be stored. 18" Ceiling Clearance Required Ensure that there is enough clearance from the top of the ceiling when deciding what storage location to go with. The 27 gallon storage bin pictured requires at least 18" of clearance from ceiling to the bottom of the storage bin. Dual Bolt Connection Allows for up to 5 garage ceiling rails to be securely connected together for seamless storage. Safety Bolt Included bolts can be installed on opposite corners of the rails to ensure the bins will remain in place while being stored. Secure into 16" or 24" ceiling studs Ensure the ceiling rails are secured tightly to the studs in the ceiling to get maximum storage capabilities. Do not secure only though drywall Not securing the ceiling rails to the studs could lead to lack of support and failure of the ceiling rails.