Excerpt: The Britax Parkway SG should be on retail shelves in July. No, it’s not the old Parkway booster with new fashions; it’s an entirely new product. The Parkway Secure Guard (formerly known as Slide Guard) is rated for kids 40 to 120 pounds and a standing height of 38 to 63 inches. The top seated shoulder height with the backrest is listed as 21.5 inches. The Parkway SG converts from an adjustable high back to a backless booster.