Ball Cup, High Friction with Rubber.
At least, that’s what Brickset and the LEGO Group call it. The name is a little awkward. And a little suggestive. Bricklink refers to it as a Hero Factory Arm/Leg Extender with Ball Joint and Ball Socket. Neither of these names is particularly catchy.
I first encountered this piece when putting together the new Creator set 31085: Mighty Dinosaurs. While this is the first Creator set to feature it, it is by no means a new piece.
Appearing initially in 2012, this piece has featured heavily on the constraction figures, with themes such as Hero Factory, Bionicle 2: the Rebirth; Star Wars; Chima and DC Superheroes. More recently is has appeared in several Ninjago sets and a couple of NEXO Knights sets, particularly those involving dragons or mechs, as well as the ClayFace Splat Attack (70326,70327,70593,70595,70627 and70904). It was also present in 75156 Admiral Krennic’s Shuttle Craft, from Rogue One. Having little experience with buildable figures such as Bionicle and the like, and having not put together the mech sets and large dragons from Ninjago, I was unlikely to have encountered it until now. Continue reading