Milestone Capes can be worn once you reach certain total Experience amounts. These capes are purely cosmetic, offering no bonuses, stats, or perks.
You can make them by bringing the requisite number of balls of wool, as well as 10M coins, to the Loom on the farm between Falador and Port Sarim. New capes are unlocked at the following thresholds, and require the following number of balls of wool.
For an entire cape set, you will need: