The Thule Sleek can be used in 13 different configurations as a single, double or twin stroller by using different combinations of the seat, bassinet or car seat accessories. A list of these approved configurations can be found in the product manual.
The Sleek should only be used for configurations shown in the manual. Any configurations not found in the manual are not approved by Thule testing and safety standards.
The Thule Sleek Adapter Kit is included with a purchase of the Sleek Sibling Seat or Bassinet. it includes one set of upper and lower adapters. There are no additional purchases required to configure the Sleek as a double or twin stroller. A Sleek Car Seat Adapter is needed for each car seat attached to the stroller in addition to the Sleek Adapter Kit.
The Bassinet, car seat and main seat should only be mounted to the upper adapters when a seat or bassinet is mounted to the lower adapters as well, according to approved safety standards.
When carrying multiple children, the heaviest child should be positioned closer to the rear wheelbase. This requires that the heaviest child be placed in the upper seat.