BAL X-Chock Tire Locking Chock locks wheels by applying force to both tires. Aids in trailer stabilizing and prevents tire shifts. A hand-operated plated ratchet wrench (Model 841025, included) turns a drive nut, extending the chocks against the tires for locking and retracting the chucks for removal. Fits even the tightest of applications retracting down to 1 3/8" and extends to 10". Opens to 10 inch. Provides added stabilization and prevents tire shifts by applying opposing force to tandem, tire applications. As opposed to other chocks, the X-chock works with the tires natural movement instead of against them. Fits even the tightest of applications retracting down. Rust inhibitive coating and is plated ratchet wrench with comfort bumper.