A difficult 6 x 6 x 3 puzzle consisting of a ring and four identical blocks.
Fit the blocks into the ring and slide them around to make the final shape. No rotations required.
Original design at http://puzzlewillbeplayed.com/663Ring/Intrude2/
I have included the .xmpuzzle file which can be loaded into Burr Tools if you need help with the solution.
Print one of the rings and four copies of the block.
The STL files have been designed based on 10 mm unit cubes with a 1 mm bevel and a 0.1 mm offset to allow easy movement of the pieces.
I printed mine with 0.2 mm layer height, two perimeters and 20% infill, four bottom layers and six top layers should ensure that any irregularities in the top surface get smoothed out.