This Sliding Puzzle Tower consist of 2 segments that can be rotated independently. This puzzle have 6 row of tiles with 6 different colour (red, orange, yellow, green, blue, and purple). The segments also has colours, wich means every row of colour has a specific place.The lower segment contain 18 tiles that consist of 6 row. The upper segment contain 3 tiles and consist of 6 rows, in which 3 rows are left empty to give an empty slot to move the tiles. This gives you a total of 21 tiles that's need to be rearranged to solve it.
Here is some more closer look for the parts.
(From left to right) The lower segment, the upper segment and one of the tile: