Polyethylene construction - taste-free tube lets the true taste come through. NSF-51/61 certified. Tubing complies with FDA Regulation 21 CFR 177.1520 (c) 3.1 b for food contact under conditions of use D through H in Table 2 of 21 CFR 176.170 (c).Numbered (Series 224) - promotes proper line connections in multiple tube applications.