Comes with allen wrench for locking and unlocking.  Dimensions: 5.5" across (outside) (13.97 cm) 3.75" across (inside) (9.52 cm) 17.5" around (outside) (44.45 cm) 14.25" around (inside) (36.19 cm) 1.25" o-ring opening (3.17 cm) 11.1 oz / 314.67 grams