Our clip on shades have fitters that clip on to standard bulbs (E26) or a candelabra bulbs (E12).
We have many in stock clip on shades with clip on fitters already built on.
Hundreds of other lamp shades can have clip on fitters quickly added in seconds, just ask.
Clip on shades make sense for many small lamps that would otherwise require a special short harp and a very small special light bulb not readily available. Clip on shades work with all popular bulbs and do not require special hardware or special bulbs.
Also see: clip on sconce shades and clip on chandelier shades