Universal top plate is 2" x 6" pre-drilled and tapped to fit most u-shaped mounting brackets. Pivots at top & bottom of mount using Lift & Turn mechanism for twice as many adjustments. Lift & Turn base has 360 degree rotation every 18 degrees. 6 locking positions up & down in 90 degrees with stainless steel plunger assembly. 8", 10" & 13" tall. Base plate of the mount can be used with the thumb screws in the track OR you can used use the four corner drilled holes to hard mount with permanent mounting plate (sold separately) for those who are not using the track system.