We ran across these little gems when we were researching a miniatures project here in our shop. These are solid micro grain carbide, 1 1/2" overall length, two-flute, flat-bottoming end mill cutters with a 1/8" shank.  We offer an 1/8" to 1/4" collet adapter made by Onsrud Cutter. Due to the more brittle nature of carbide, the cutting edge length is always three times the cutting diameter.  Our Micro Bit Kit consists of the following six diameters:

1/64 (.015"); 1/32 (.031"); 3/64 (.047"); 1/16 (.062"); 5/64 (.078"); 3/32 (.093").

Individual bits and custom sizes ranging from .001" to .125" are also availabe on special order.