Supercast SW20 is a 10mm x 20mm swellable waterstop that can be installed and positively linked into conventional Supercast PVC waterstop networks. Supercast SW20 is made from high performance synthetic elastomeric strips. The swelling action is the result of contact between water and hydrophilic groups which are part of the Supercast SW10 ‘Basic polymer’ molecular structure. These hydrophilic groups are not subject to extraction and loss of swelling performance by prolonged or repeated wetting.