The Trailblazer is designed to be a standalone container.  The Big Square Dippers are smaller, can be used independently or inside the main compartment of the Rover, Shuttle or Launch.
Trailblazer: 5.63 x 5.63 x 1.6 in.
Launch Shuttle Big Square Dipper:  4.17 x 4.17 x 2 in
Rover Big Square  Dipper:  4 x 4 x 1.4 in