These durable track ends are machined from a single piece of aluminum. The integral 40 mm Carbo Airblocks with free-running Delrin ball bearings allow for easy adjustment when you move the car in a strong breeze - which is when you want the traveler to work at its best.ESP end controls are value-oriented options for the installation of 2:1 to 5:1 systems. Designed for strength and durability, controls feature axle bearing sheaves with sideload ball bearings.Camcleats located on the end control provide convenient, precise positioning of the traveler car, without the clutter of a separate deck-mounted cleat. When deciding on a purchase system, expect the load on the control line to be approximately 20% of the load on the mainsheet block. For most cruising boats, this will mean designing a 4:1 (or even higher) purchase system to keep control line loads in the reasonable 30 to 45 lb range. Harken purchase recommendations when using 27 mm traveler control blocks: Use a 2:1 purchase for boats with sail area under 125 ft (12 m) Use a 3:1 purchase for boats with sail area from 125 ft to 200 ft (12 m to 19 m) Use a 4:1 purchase for boats with sail area from 200 ft to 250 ft (19 m to 23 m)