Made of low-density polyethylene (LDPE) for superior quality, strength. Innovative Flex Ink won't fade, crack or peel. Wide mouth for easy refilling. Clear leak-proof cap with built-in nozzle included. Self-venting design eliminates leaks & dripping. The low-density polyethylene plastic is very responsive, with a smooth bounce back that won't get stiff over time. Easy to control squeeze for dispensing.