The reflector screen kind of does both. Kindof complicated to describe it more accurately. Basically it doubles gain in one direction while reducing gain from the backside.
The blocks are PVC which isolates the elements and transmission wires from the metal mast (which leads to ground) as this would short the electrical transmission of the signal, and seriously reduce the performance. It is also hydrophobic which is also advantageous on the electrical transmission side, when it gets wet from the rain.
It's pretty sweet, all Zinc Galvanized (screws and washers are plated) Steel with PVC blocks. Mounts to a mast with standard hardware...wall mounts, eaves mounts, the works. Screen is easily removed if you want a more bi-directional pattern.
It even has quick wingnut mounts for the matching transformer.
Epson 8350 / Panasonic AX-200u / Optoma Graywolf 92" / Draper Luma 92"
Samsung 51F8500 / Panasonic P50ST60 / Vizio P502ui-B1 / Sony 50W700B LCD
Sony S790 / Panasonic BDT-220 / Roku 2 XS & Roku 2
Samsung F550 / Speakercraft CS3 / Yamaha YAS-105