A downhole tool body includes an outer surface having at least one O-ring gland. The at least one O-ring gland includes a first contour having a first radius greater than about 0.035″ (R0.89 mm) and a second contour having a second radius greater than about 0.035″ (R0.89 mm). A backup ring is arranged in the O-ring gland. The backup ring includes a gland contour having a radius that is complimentary to the first radius.