HBB with IsoFix

[RandomUsernameHere]

I'm planning to get a HBB with IsoFix (such as the Maxi-Cosi RodiFix Air Protect, but any recommendations gratefully received). The vast majority of the time it will be used in the back of my car, which has IsoFix, but is it also safe to use it with just the car seatbelt? It might be useful on the odd occasion such as travelling in friends' cars, which may not have IsoFix.

Isofix on any high back booster is optional - it just holds the seat in place when there's nobody in it. If there's no isofix in the car, you just need to fasten the seatbelt to hold the seat in if there's no child in it.

Great, thank you so much!