There are three kinds of TMB: 

1. TMB compound (CAS 54827-17-7), white powder, purity 99%, it is a material for preparing TMB substrate.  

2.  TMB two component substrate solution, they are two bottles of colorless liquid. They can be used directly for ELISA. They are the product prepared from TMB compound.  

3.  TMB single component substrate solution,  It is colorless liquid. It can be used directly for ELISA. It is the product prepared from TMB compound.