The J311CL is a 1/4 oz clear PS plastic thick wall jar with 33-400 neck finish. Thick wall jars are 1-piece jars with thick walls. More material goes into making these thick wall jars, giving them heft and a raise in elegance. This jar is made of polystyrene (PS). PS is light-weight, hard, and has an almost glass-like appearance. It is shiny and classy. It has limited flexibility and is more brittle than other plastics. Essential oils may damage polystyrene, causing products to leak. Products with essential oil content will work better in PET or glass containers. This jar is typically used for lotion, cream, serum, gel, putty, clay, hair products, skin products, cleanser, and other personal care products. This jar has a 33-400 neck finish, and will fit closures with the same 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.