The Grid-Lok is a stackable rebar chair designed for single or multilayered reinforcement. Made of non-corrosive, injection-molded plastic, it eliminates tie wires and won't damage epoxy-coated rebar. With heights starting at 1 inch, with 0.5-inch vertical increments, it can fit #3, 4, and 5 rebar. Oxford Industrial Technologies. 203-268-6030. www.oxfordtechusa.com .