These Nylon Twin Wheel casters are perfect for wood base office and task chairs. The stem is a 5/16" x 1-1/2" Grip Neck, or Wood Stem. They include the metal socket which is hammered into the pre-drilled 3/8" hole in the wood. The nylon body construction provides for capacity at 100 lbs each, so these little casters can handle quite a load. The bodies are designed to take common abuse from office and shop enivronments.