Interchangeable choke tubes allow you to vary the spread of your shot pattern to properly engage targets near and far. Most guns come with at least three tubes, although the Remington 870 Express comes with only a Modified choke. Usually guns come with an Improved Cylinder for close range, a Modified for medium (25-35 yard) range, and a Full for long range. Those three chokes will also see you through your first rounds of trap, skeet and sporting clays. If you want to add, say, a wide open Skeet choke for the close-range game of skeet, or if you need IC and Full to round out the selection for your Express, Redhead Choke Tubes cost around $20 and fit a variety of guns.