The Baby Snug is a 2 piece seat that grows with your baby:
1st stage – when baby has head control (approx 3 months)
2nd stage – when baby outgrows the 1st stage seat (approx 12 months) – remove the inner seat for stage 2
The BabySnug is pricey at $59.99 but due to the 2nd stage, it can be used for a longer period of time than other seat positioners. The one common commentary is that the Baby Snug runs big so a smaller baby may slouch in it even with the seat insert.