This was one of the packs of extra specialist Lego pieces available via mail order back in the day - or in the toyshop in the centre of our city, to our great fortune. I believe this purchase was made after buying the Legoland ideas book, as these pieces are featured in some of the instructions for vehicle construction in the book. The challenge then was to build correctly to these instructions and then transfer the learning to self-designed vehicles, learning how to construct them so that the couplings meet up correctly. A second vertical hinged joint in place of one of the ball-and-socket joints would have been preferable however, and would have served as an incentive to step up the scope of self-designed building.