Sketch pens that clip together. Colors are completely washable. Contains 40 percent more ink and lasts longer. Child safe: Food grade ink. Ventilated caps which are child safe. Click seal cap which prevents drying. Medium point tip for good ink flow. Contains free connector which helps in giving angles to the models. Special skin and grey Color, 2 black pens for outlining. Connector pens are easy to store and hard to misplace