A non-metallic element system is provided as part of a downhole tool that can effectively seal or pack-off an annulus under elevated temperatures. The element system can also resist high differential pressures without sacrificing performance or suffering mechanical degradation, and is considerably faster to drill-up than a conventional element system. In one aspect, the composite material comprises an epoxy blend reinforced with glass fibers stacked layer upon layer at about 30 to about 70 degrees. In another aspect, a mandrel is formed of a non-metallic polymeric composite material. A downhole tool, such as a bridge plug, frac-plug, or packer, is also provided. The tool comprises a support ring having one or more wedges, an expansion ring, and a sealing member positioned with the expansion ring.