Hi Chelsea, Thank you for your enquiry. The ISOFIX/LATCH restraints are an international standardised mounting system for groups 0+ and I child seats. In the vehicle, appropriate Isofix anchors are permanently mounted to the body-shell. These standardised mountings enable an Isofix base to be anchored simply and quickly. Weight restrictions for Isofix can vary depending on the vehicle and car restraint being used. We would always recommend checking the manual for both the vehicle and car seat before installation. With regards to The Evenflo Securekid Combination Booster this particular seat is to be used with ISOFIX up to 18kg and then with use of a seat belt after this. If you follow the link https://www.babyonthemove.co.nz/store-locations/ this will take you to our online store finder where you can find contact details for your nearest Baby On The Move Store. Here, one of our expert Car Restraint Technicians can assist in helping you to find the right car seat for you, your child and advise on correct installation. We hope this has helped with your query.