The Amazing 3D Puzzle Ultra by TCC (GV$7)

Comes with a $7 gift voucher on your next purchase :) 
 
The ultra Rosewood model of The Amazing Puzzle 3D that's all in solid Rosewood, including the box.

Besides, there's an additional gimmick in The Amazing Puzzle Ultra, allowing you to perform this effect with minimal sleights of hands.

It's not just a puzzle but a magic secret is involved.

You show a block puzzle that fits snugly into an outer box. The blocks are poured out and rearranged.

You then add two extra pieces one by one, each time you can rearrange the blocks into a rectangle. After two extra pieces are added to the puzzle, amazingly, the shape and surface area remains the same, and the entire puzzle still fits into the exact same solid rosewood box it came out of.

Dimension
Overall Size: 8cm×6.6cm×4cm
Features
All in solid Rosewood including the box.
Very portable size.
Special gimmick for easier performance.
Full online instructions.