Manhole riser rings from LADTECH can be installed in minutes. The rings nest together and include a 2 percent slope ring and a 1/4-inch spacer ring for a precision fit. They’re made of high-density, lightweight recycled polyethylene; meet AASHTO’s HS-25 axle-loading spec; and are impervious to H2S corrosion that destroys concrete. 877-235-7464; www.ladtech.com.