Designed and made by Bill Cutler; can't be disassembled.
(Red Oak, 4.5 inches)

From his computer analysis, Cutler determined that 139 was the largest number of states that a standard 6 piece burr could have without having a solution, and then he chose the simplist of these for this puzzle. So this burr is made to the dimensions of a normal 6-piece burr, has lots of movement, but can't be disassembled (it was made by gluing two portions of a piece together during assembly). Here is his diagram of the pieces: