The molecular weight displayed in the Tocris catalog and website represents the product as shown by the chemical structure.
During manufacture it is common for water of hydration to be incorporated with the product. The degree to which this occurs can vary from batch to batch and as a consequence the molecular weight of the material supplied can change. Additionally, we may add or change a salt from that stated in the catalog. Any change is clearly stated on the vial labels and accompanying product datasheets; any variation should not affect the basic pharmacological properties of the compound. Consequently solutions should only be made up using the molecular weight as stated on the product datasheets and vial labels.