An ongoing demonstration project has shown the feasibility of using slender (90 mm x 90 mm x 2.4 m) recycled plastic pins (RPPs) for in situ reinforcement of slopes and embankments. The technique uses RPPs driven into the face of the slope in a grid pattern to intercept the sliding surface and pin the slope. The engineering properties of the RPPs, including the compressive, tensile, and flexural strength along with creep behavior, dictate the design and construction practice. Constituent materials and manufacturing processes are highly variable among the more than 30 U.S. manufacturers. A specification for acceptance of the members is needed; however, before an effective specification can be developed, the appropriate engineering properties and design requirements for the RPPs must be determined. The engineering properties and driving performance of four different types of members were evaluated and are reported on. Additional evaluations are under way.