What is Single to double?

Single to double describes a stroller chassis that accepts one seat or a pair of seats, so you can start with a single and add a second for a second child or a newborn. Baby Jogger, Baby Trend and Bugaboo all state that they offer it, which makes the choice about seat options and price rather than about capability. Bombi and Bumprider state that they do not, so their strollers stay single seat. Buying a convertible chassis usually costs more than a single stroller, so weigh it against how long you expect to carry two children.