Laws of Cricket 1947 Code (Fourth Edition) - Law 8
The wickets shall be pitched opposite and parallel to each other at a distance of 22 yards from stump to stump. Each wicket shall be 9 inches in width and consist of three stumps with two bails upon the top. The stumps shall be of equal and of sufficient size to prevent the ball from passing through, with the tops 28 inches above the ground. The bails shall be each 4 3/8 inches in length, and, when in position on the top of the stumps, shall not project more than 1/2 inch above them.
Notes on Law 8
1. Except for the bail grooves the tops of the stumps shall be dome-shaped.
2. In a high wind the captains may agree, with the approval of the umpires, to dispense with the use of bails (see Law 31, Note 3).
Reproduction of the Laws of Cricket is by kind permission of Marylebone Cricket Club