The TNR23G821K from United Chemi-Con is not a part we carry. A possible alternate is 495-4662-ND (EPCOS - TDK Electronics B72220S0511K101). Please review the specs/dimensions from the datasheet SIOV metal oxide varistors, leaded varistors, StandarD series (tdk.com) before ordering.
The TechForum Cross Reference category is for parts that Digi-Key does not sell or parts that have gone obsolete. Our Engineers and Techs have reviewed the specifications for these parts and made a recommendation for a replacement. Please review the suggested part to ensure it will work for your application.