*PLUMBERSSTOCK EXPERT* responded:
Thank you for asking us at Plumbersstock.com about the Mars 21787! Yes, this kit fits the Mars 21780 condensate pump. To begin the ordering process, please click the Add to Cart button, enter your zipcode and your billing information, and we will take care of the rest. Please refer to the specification sheet if you have more questions about the Mars 21787. Happy Shopping!