Hi. Good question. Most infant only rear facing seats that come with a base are designed to also be installed safely without the base. Check the seat's manual to be sure. When you install the seat without the base, pay special attention to the recline angle of the seat. Achieving the correct recline angle without the base can be tricky sometimes. If the seat sits too upright, you can place a "swimming noodle" that is cut to length under the child seat to help you achieve the correct angle. You can use up to 3 of these noodles, taped together in a sort of pyramid. If you don't have a noodle, you can use a tightly rolled and taped towel in the same fashion.