Broad arrows can be purchased from any Slayer Master, and are the only arrows which can be used to slay Turoths and Kurasks. They are stronger than mithril arrows, but weaker than adamant ones.
You can only wield them if you have a Slayer level of 55 and a Ranged level of 50. They can be shot from magic bows or higher.
Making broad arrows is learned from Slayer Masters for 300 slayer points. Broad arrowheads can be bought from Slayer masters, which are then attached to headless arrows. It requires level 52 Fletching and yields 10 Fletching experience per arrow, or 150 experience per set of 15. Up to 35,000 broad arrows can be made per hour which is equal to 350,000 experience.
Fletching broad arrows is a common method for ironmen to obtain Fletching experience, as the broad arrowheads can easily be bought in bulk while other metals take longer to collect and smith into arrowheads.