查了下，是item level
官方网页：
http://www.battle.net/diablo2exp/quests/rewards.shtml摘要：Normal items add the max number of Sockets depending on the item's level (this is determined by the level of the monster that dropped it) and the inherent maximum number of Sockets for the item's base type. So you may not always receive the "max" number of Sockets.
google结果：
==============================
物品 Ilvl 孔数限制
------------------------------
Body Armor 1-25 3
26-99 4
------------------------------
Shield 1-39 3
40-99 4
------------------------------
Scepter 1-24 3
25-39 5
------------------------------
Staff 1-24 5
25-99 6
------------------------------
Bow 1-24 3
25-39 4
40-99 6
------------------------------
Ama Bow 1-24 3
25-39 4
40-99 5
------------------------------
Axe 1-24 4
25-39 5
40-99 6
------------------------------
Club 1-24 3
25-39 4
40-99 6
------------------------------
Sword 1-24 3
25-39 4
40-99 6
------------------------------
Hammer 1-24 3
25-39 4
40-99 6
------------------------------
Knife 1-24 2
25-99 3
------------------------------
Spear 1-24 3
25-39 4
40-99 6
------------------------------
Ama Spear 1-24 3
25-39 4
40-99 6
------------------------------
Polearm 1-24 3
25-39 4
40-99 6
------------------------------
Crossbow 1-24 3
25-39 4
40-99 6
------------------------------
Mace 1-24 3
25-39 4
40-99 6
------------------------------
Helm 1-39 2
40-99 3
------------------------------
Claw 1-24 2
25-99 3
------------------------------
Orb 1-24 2
25-99 3
------------------------------
Nec Shield 1-24 2
25-99 3
------------------------------
Pal Shield 1-24 3
25-99 4
------------------------------
Bar Helm 1-24 2
25-99 3
------------------------------
Dru Helm 1-24 2
25-99 3
------------------------------
Circlet 1-24 1
25-39 2
40-99 3
