Bases are common (white) items — runewords only form in them. Sockets are a per-item stat rolled within a range (e.g. "Sockets 0–3"), decided on drop, capped at 6. Ranges for unique items are listed on the item pages (the "Sockets" affix line); no data source publishes the socket range of white bases — neither the game client data nor either community database carries that field, and the only base with a stated count is the Socket Ring (fixed 1). For reference, the highest socket counts seen on uniques: weapon / body armor / shield 6, helmet 5, boots and charm 4, gloves and belt 3, ring and amulet 1. A base exists at several tiers (a tier is a stat and level band, not different art); tier level gates: D=1, C=16, B=26, A=40, S=52, SS=71 — click a base name to expand its per-tier values.