When installing an iZi Flex FIX i-Size on an outer vehicle seat, you can take the inner SIP bumper off in order to be able to fit several seats/people next to each other. When installing an iZi Flex FIX i-Size in the middle position in the vehicle, both SIP bumpers can be taken off if you would like to place other seats/people next to the iZi Flex FIX i-Size on both sides. When installing an iZi Flex FIX i-Size in the middle position in the vehicle but are only placing another seat/person next to it on one side, we recommend you to keep the other SIP bumper on the iZi Flex FIX i-Size.