Earplugs
Don't take your hearing for granted. The human ear is a delicate and fragile thing and you need to look after it as much as possible. If you do loud gigs earplugs can be one of the most important pieces of DJ kit you have.
Cheap disposable foam earplugs are no good. Get a set of good earplugs that let through as much of the dynamic range as possible, just at a lower volume:
Custom moulded earplugs are also available for the best protection.
