Chesterton 8K a stacked v-ring set with a positive-rake design to provide optimum operating performance. Unlike conventional stacked sets, this design makes contact through the center to ensure even loading, longer sealing life, and minimal gland pressure.Chesterton 27K a single-acting, stacked v-ring set with a positive rake design to provide optimum operating performance. Unlike conventional stacked sets, this design makes contact through the center to ensure even loading, longer sealing life, and minimal gland pressure.