The basics This Preval Bottle is a 6 oz glass reservoir jar (and polypropylene safety cap).  The Pro Tip The 100% glass reservoir is easily cleaned, reusable and recyclable. Glass is inert and will not leach. The benifits Preval’s glass reservoir was specially designed to withstand the impact of an 8 ft. drop onto concrete. The bottom line The glass reservoir safely stores volatile liquids such as varnishes, oils and paints.