Created exclusively for use with doulton single and multi-stage undercounter water filter systems, this white plastic tubing helps you get the best from your system. If you need any replacement tubing, this box contains 1.5 Metres with 1 4 idx 3 8 od john guest specification. 1.5 Metres of lldpe white plastic tubing only recommended for use with doulton single and multi-stage under counter systems. Specification: 1 4 idx 3 8 od john guest