Almost any 13" laptop (MacBook Pro, MacBook Air etc) plus some particularly small and slim 14" and 15" models in it's padded laptop compartment (check dimensions very carefully). The 14" MacBook Pro does fit.

In the included half size insert: Most DSLRs (e.g. Canon 5D, Nikon D850 without battery grip) with small-to-medium lens attached and maybe a spare lens.

In the included half size insert: Almost any mirrorless camera (Sony A7IV, Fujifilm X-T4, Nikon Z7, Canon R6 without battery grip etc) with with small-to-medium lens attached and maybe a spare lens.

In the included half size insert: Any rangefinder camera (e.g. Leica M10) with almost any lens attached. With room left for an extra lens or maybe a second camera.

In the optional full size insert: Most DSLRs or mirrorless cameras with a small-to-medium lens attached (e.g. Canon 1DX, Canon 5D, Nikon D850, Canon R6, Nikon Z7 etc). Plus 2 to 4 lenses (tall enough for a 70-200mm not attached to the camera).

In the optional full size insert: Some medium format cameras such as the Hasselblad 500CM with 80mm attached, Fujifilm GFX-50S with small to medium lens attached, Hasselblad H6D with small lens attached etc. Plus room for extra lenses.