Vector Laboratories TMB Peroxidase (HRP) Substrate Kit, (3,3Æ,5,5Æ-tetramethylbenzidine) produces either a precipitating blue reaction product or a soluble blue reaction product, depending on whether a stabilizer has been added to the solution. This sensitive chromogen can be used for blotting, immunohistochemical, and in situ hybridization applications. TMB stained slides can be dehydrated and permanently mounted. The soluble blue product, produced in the absence of the stabilizing solution, is useful for ELISA assays.