The semi-permeable membrane, created from a natural source of cellulose, allows passage of particles up to 14,000 molecular weight standards. Each length is packed in heat-sealed plastic bags to prevent contamination. • Choice of widths & lengths • Packed in heat-sealed bags • Made from natural cellulose Unique to Science First®! Our proprietary, customized machine allows us to manufacture small rolls of dialysis tubing in the configurations you need! Click here - dialysis tubing [https://store.sciencefirst.com/catalogsearch/result/?q=dialysis] - to see our standard sizes. If we don't stock the length you need, give us a call for a custom quote.