Moddified created center hole .

Summary
Customized version of https://www.thingiverse.com/thing:3802943

Created with Customizer! https://www.thingiverse.com/apps/customizer/run?thing_id=3802943

Instructions
Using the following options:

$fn = 20
inc = 30
tube_r = 20
ball_r = 25
tweak_ball_r = 20
tweak_spac = 45
shell_off = 0
shell = 25
inner_edge = 55
flat_bottom = 1
add_base = 1