Extralink PEGDA is a thiol-reactive crosslinker designed for use in HyStem-C and HyStem-HP kits. Pack comes with Buffer B. HyStem V2.0 kit components are reconstituted with a buffered 1X PBS. The resulting components will also result in a pH neutral isotonic salt hydrogel. The ending pH, osmo, and rheological properties are the same from Version 1.0 to Version 2.0. Extralink is polyethylene diacrylate (PEGDA) with a molecular weight of 3500 Da. It is a thiol-reactive crosslinker that covalently reacts with the thiol groups in Glycosil, Heprasil and Gelin-S to form viscoelastic hydrogels. Extralink vials are >80% acrylated and supplied as the crosslinking component in all HyStem hydrogel kits. Extralink vials are paired with HyStem-C and HyStem–HP kits while Extralink-Lite vials are paired with HyStem hydrogel kits to provide comparable experiences despite the different HA concentrations.