An ultrasonic fluid flow meter can include a casing structure including a hook portion configured to engage a conduit to secure the casing structure to the conduit. The ultrasonic fluid flow meter can include a transducer block disposed within the casing structure and seating ultrasonic transducers. A distance between the hook portion and the transducer block along a direction transverse to the transducer block can be adjustable. The ultrasonic transducers can face the conduit when the casing structure is secured to the conduit via the hook portion.