This set is perfect for a student starting organic chemistry. You can build hundreds of different open and closed models. It is an equivalent (but more cost effective) alternative to 3B W19721 -- featuring the exact same atoms in the same quantities. 114-Piece Set 50 Atoms 12 Black carbon (4 holes) 20 White hydrogen (1 hole) 6 red oxygen (2 holes) 4 blue nitrogen (4 holes) 4 green halogen (1 hole) 2 yellow sulphur (6 holes; 4 holes) 1 purple phosphorus (4 holes) 1 gray metal (1 hole) 64 Links 28mm Gray links (26) 43mm Gray links (12) 28mm White links (26) Assembly tool