Just some spherical doorknobs. Suitable for traditional British quarter inch or 7mm square bars, diameter 45mm.

3 styles:- Plain, with circular divots like a golf ball, and a high tech 'deathstar' kind of texture of interlocking rectangles. 

The knobs take M3 x 20 screws, with a captive nut,

There's a rose/collar too to help keep the door surface clean? ( really have no idea what purpose they serve, but every knob seems to have one!)