An ultrasonic meter (28) for measuring a flow-rate of a fluid is described. The ultrasonic meter (28) includes a flow conduit (5) for the fluid. The flow conduit (5) extends along a first axis (6) between a first opening (7) and a second opening (8). The ultrasonic meter (28) also includes one or more pairs of ultrasonic transducers (2, 3). Each pair of ultrasonic transducers (2, 3) is configured to define a corresponding beam path (9) intersecting the flow conduit (5) within a measurement region (12) of the flow conduit (5). The measurement region (12) spans between a first position (z1) and a second position (z2) spaced apart along the first axis (6). One or more portions of the measurement region (12) which are outside of any of the one or more beam paths (9) correspond to non-sampled volumes (12b). The ultrasonic meter (28) also includes one or more protrusions (34) extending along the first axis (6). At least part of each protrusion (34) is arranged to exclude fluid from at least part of one or more non-sampled volumes (12b).