No, The Brother TN433BK Toner is not compatible with the Brother MFC-L3720CDW. The compatible toners for the Brother MFC-L3720CDW are: Standard Yield TN229BK, TN229M, TN229Y, TN229C and High Yield TN229XLBK, TN229XLC, TN229XLM, TN229XLY.
Below is a link to our web page in case you would like to place the order online.
Web Page: https://www.brother-usa.com/home