Customized version of http://www.thingiverse.com/thing:299663

Created with Customizer! http://www.thingiverse.com/apps/customizer/run?thing_id=299663

Using the following options:

diameter_top = 8
diameter_bottom = 5
height = 30
outer_diameter = 20
nut_diameter = 6.25
articulation_thickness = 1.5
pressure_point_thickness = 4.5
bolt_diameter = 3
opening_width = 2
washer_diameter = 5.5