1,receiving signal strongly 2,gain can be produced on your need 3. ... main material is Oxidation aluminum alloy , this material can more effective to prevent the antenna outdoor from acid ... The yagi antenna have well-presented , easy install and can work long time outdoor. Specification Specification : Input Frequency: ... :7dBi,9.5dB,11dB,12dB,13dB,16dB. (can select) Front to back ratio:≥12dBVSWR:≤1.5Input ...