Graco Booster Car seat

Hi Mary-Ellen, thank you for your enquiry. The width of a Graco Booster Car Seat is 43cm, with the base width at 40cm. If you can measure the gap between the two Dionos you currently use that should give an indication as to whether it will fit in the space you have. If you have any further queries on this, feel free to pop into your nearest Baby On The Move store and they will be only happy to help you furrther. Follow this link to find your nearest store: https://www.babyonthemove.co.nz/store-locations/. I hope this has helped with your query.