Conventional type - not ridesafer vest or bubblebum. It's for 6.5 ds, 50lbs, outboard in 2011 nissan altima next to recaro performance sport in center (grandma's car). He's currently using the RSTV but it's getting a little snug on him, and if we could squeeze in a regular booster I think that would be easiest - not sure they could handle the bubblebum. It's on the driver's side side where he can't unbuckle the center seat. If nothing will fit I guess I can do bubblebum.