A steerable laser probe may include a handle, an actuation structure, an optic fiber, and a housing tube. The wall block comprises an interior face for forming an interior surface of a segmental retaining wall, an exterior face for forming an exterior surface of the segmental retaining wall, first and second sides that extend from the exterior face to the interior face, and a top surface and a bottom surface. The wideband polyphase filter has poles corresponding to a first filter frequency and a second filter frequency, where the two filter frequencies are different. 2 m to 12 m on the average, a hydrophilic property of the cut part improves and the stain of a frame can be decreased. The second support member extending along a longitudinal axis disposed transverse to the first support member.