Glide Gear DEV 4 Camera Dolly System 4Ft Rails, Sled w/ Track Wheels & Track Ends (2) 4 ft aluminum rails 2) aluminum track end mounts with 1/4 20 & 3/8 taps 1/3 inch thick aluminum sled plate with three heavy duty wheel mounts and 28 accessory mount taps for a wide range of accessory mounting