These clear containers are single wall jars. They are different from the 2 piece double wall jars. Made of PET, they are a great option for lab samples or food products as the clarity is high and they are impact resistant. Avoid using PET containers to store products that contain essential oils greater than 5% or fragrance oils greater than 15%. These jars are a great option for hair products, lotions, creams, putty, clay, skin cleanser or other personal care products.