Spherical sealed speaker housing. This is designed for the Dayton Audio 4in woofer and passive radiator but can be tweaked to suit your needs as long as the passive radiator matches the driver. I printed at 55% infill as the sphere is mostly hollow. The opening for the switch is 20mm and the bottom is designed to snug fit 2x 26x10x8 bearings sop that the speaker would smoothly rotate if so desired.