The DP634WH is a white PP plastic 18-415 smooth skirt dispensing treatment pump with 3.75 inch dip tube and clear plastic overcap (0.13 cc output). Treatment pumps are fitted with a clear overcap to prevent accidental dispensing. This closure fits containers with a 18-415 neck finish. The first number is the diameter of the container's opening (in mm). The second number refers to the thread/style/depth of the closure's skirt. This pump is made of polypropylene (PP), which means it has a high heat tolerance level and an excellent resistance to fatigue. Dip tubes can be trimmed to fit smaller shorter containers.