It is a conventional, low-wing cantilever monoplane and essentially an enlarged version of Piel’s successful Emeraude, designed to accommodate more passengers. This extra capacity is provided by a redesigned fuselage which is higher in the rear section and longer overall. While the Emeraude has only two seats, side-by-side, the Diamant has an extra bench seat at the rear of the cabin to seat one or two more people. The wingspan is also greater than that of the Emeraude, allowing for a greater maximum take-off weight.
As with the Emeraude, Piel obtained type certification for the Diamant, allowing it to be manufactured on a commercial basis. However, unlike the Emeraude, this did not actually transpire, and the Diamant was only ever built as a homebuilt.