In the small ecosystem of “side release at the toe” hybrid tech bindings, Trab is somewhat of an outlier as it requires a boot with compatible “tech” fittings, and it’s the lightest weight of such bindings. The heel does not function as a step-in (when entering in downhill mode, you hold it open by pressing down with a ski pole).
Note: As of 2017, two different types of boot fittings have been available in the wild. S3 was the first, and was not compatible with “Dynafit” type tech bindings. The latest, S4 fitting, is ingeniously built to function with all tech bindings as well as Trab TR2. We tested the S4 fitting. It works well. We found in our tests that it yielded about 1/2 a DIN number less release-retention tension. If you fine-tune your binding settings keep this in mind.
TR2 ski binding by Trab, requires a dedicated boot with special fittings.
Site search for Trab TR2 ski touring binding information.