The M659BK is a black PP plastic 18-400 ribbed skirt child-resistant dropper assembly with rubber bulb and glass pipette (fits 10mL bottle). Dropper assemblies are composed of a number of parts: the cap, the bulb and the pipette (tube). The pipette length is 55.5 mm (2.18 inches). Dropper assemblies are used with liquids that require precision and intricacy when using the product. This closure has been equipped with a child-resistant feature. Polypropylene (PP) is marked with the resin identification code of 5. PP is less flexible than LDPE, somewhat stiffer than other plastics, reasonably economical, and can be translucent, opaque, or of any color. PP has very good resistance to fatigue, and has an extremely high melting point (320 degrees Fahrenheit or 160 degrees Celsius).