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A max cape is a cape sold by Max in Varrock. It is available to players who have attained at least 99 in all 25 skills (it does not require 120 in Dungeoneering, however). It has an emote which shows off the player's expertise in each skill. The minimum Total Level a player needs for max cape is 2475.
The completionist cape is the most powerful cape in the game. When purchased, it comes along with a corresponding hood. It can be bought in Varrock Museum for 5,000,000 coins from the museum guard on the top floor by members who have all skills trained up to 99, and Dungeoneering up to 120, completed all quests, tasks, miniquests, unlocked all the music tracks, prayers, and magic spells. The cape can then be upgraded to a trimmed version after completing a list of requirements including 5000 Castle Wars games and a full statue of Dahmaroc in the player's house.
Max cape:
Comp:
Comp (t):
Source:
http://runescape.wikia.com/wiki/Max_cape
http://runescape.wikia.com/wiki/Completionist_cape