While LEGO itself has taken a crack at making a buildable version of K-2SO with set 75120, some people prefer to do it themselves. Josephine Monterosso has made of version of the droid using only 75 pieces, forgoing the CCBS and specialised pieces all together. A lot of clever (and illegal) connections went into this to correctly capture the shaping. Make sure you zoom in to see them all – my favourites are in the torso where a single piece gives much of the round look, and some black floatation rings are used on the shoulders.