BLegos:
BLegos are legos (blocks that attach via dots on the tops fitting into openings in the bottom) that have the additional feature of becoming traditional. There is two panels inside each BLego that slide up and lay over the circular bumps, thus rendering them blocks that do not stay together.
BLegos are based of the physical principle of friction. When the Blegos are in lego form they stick together because there is friction between the protruding circles and the sides of other BLegos. The the BLegos are in block form they have substantially less friction when stacking on each other and will easily fall apart.
When playing with BLegos, a child will first model what they are going to try to build using the block function of the BLegos and then once they are satisfied with their design, they will rebuild it with the lego function of the BLegos. This allows for mistakes to be made when designing and easily fixed, as it is sometimes difficult to get regular legos apart.
BLegos are made of plastic, so they are safe to be played with. However, they are small with some moving pieces therefore are not appropriate for children under 4. The BLegos are durable as they are made of the same plastic as legos which have proven effective many times.