WISA and NKS connectors are made of EVA (Ethylene Vinyl Acetate). EVA is a thermoplastic. EVA is formed by polymerization of ethylene and vinyl acetate (copolymer). This copolymer contains properties of an elastomer, such as flexible and soft. EVA is also a 'crosslinked' material. Crosslinking is a chemical reaction that occurs during the injection molding process in which strong bridges are formed between the long polymer chains. EVA is very durable (flexible but very tough, UV and weather resistant and wear-resistant), soft and lightweight. This makes EVA a far more effective and durable material compared to the known PVC and rubber. A product of the material EVA has the same properties both on the outside and the inside. The advantages of EVA as injection molded product: Flexible, water-resistant, durable and antibacterial. EVA products are very thermostable and have a high stress-crack resistance.
Wisa and NKS connectors are water- and airtight. The slats (support or seal rings) are very flexible, form-retaining and close perfectly. Our connectors are made from just 1 pieces and due to the excellent quality an extra rubber sealing ring is not necessary. Every loose additional part is a potential leak. Our connectors are perfectly round and have no seams. A seam or fleece formation causes leakage.
The difference between a Wisa and a NKS (a brand name bought by Wisa many years ago and always produced in our factory) connector is the inwardly folded flap (on female side of the connector). If you look at the line drawing you see two support slats and one flap. This flap covers the outlet of the ceramic toilet and pushed toward ceramic material by the two support rings. This method is not better than the NKS connector, it’s different. Some plumbers like the Wisa execution, others the NKS version.