Many gray shelving units use engineered wood (MDF or MDF composite) combined with metal frames; a smaller number list solid wood frames.
Options shown include 3-, 4-, 5- and 6-tier units, with 5-tier designs appearing most frequently.
Most listings note adult assembly is required. Some indicate tools are included, others provide only limited tools, and at least one listing specifies that tools are not provided.
Many listings include anti‑tip or anchoring hardware and reinforced supports. Several also list adjustable feet and X‑shaped or reinforced back supports to improve stability.