Patented by Rubik 1991, copyright Matchbox 1990.
(3.5 inches)

When assembled, the four sides of the pyramid are red, blue, yellow, and white. Moves consists of unsnapping a portion rotating it and snapping it back on.



Further reading:
Jaap's Page, from: http://www.jaapsch.net/puzzles/triamid.htm
McFarren's Page, from: http://www.geocities.com/abcmcfarren/math/r90/trmd0.htm
Rubik HU Patent. from: www.epo.org - patent no. HU207233