100 % cotton wool, degreased, approx. 13 g / 10 m. Cotton plugs may prolong delivery time and may therefore influence the accuracy of measurement. In tests using BRAND pipettes that have had cotton plugs inserted by a cotton plugging machine, the results were within the indicated error limits. 100 % cotton wool, degreased, approx. 13 g / 10 m. Cotton plugs may prolong delivery time and may therefore influence the accuracy of measurement. In tests using BRAND pipettes that have had cotton plugs inserted by a cotton plugging machine, the results were within the indicated error limits.