Motor mount removal to get to water pump

After removing four of the five bolts to replace the water pump I am stuck on number five. It looks like I need to loosen the passenger side upper motor mount. I need to know what size socket to use in order to remove the bolts to get to the water pump. My best guess is an 18mm and I have everything but that size and before I purchase an 18mm socket I would like some conformation. Thank you in advance for any help offered.