0.25, 0.50, 1, 2 & 4 ounce sizes are Low Density Plastic 8 ounce is High Density Plastic (HDPE) Luer lock top for leak free connection to dispensing needle, hose or other equipment Tops easily screw on and off for refill Easy to grip and squeeze for dispensing Can easily be placed upright on desk top or in a cabinet for easy access