Any car seat system you purchase should come with a detailed guidebook. This is true whether you bought an infant rear-facing car seat for your newborn, or a booster seat for your 10-year-old. Here, you can find exact specifications on when it's safe to transition your child into and out of the system based on their physical characteristics. If you can't find the information you're looking for there, then hop online and search the manufacturer's website. If you're still coming up short, then reach out to their customer service team for help. Local Missouri communities may also host drive-up car seat inspection stations, where licensed professionals can review your current setup and recommend adjustments or upgrades.