U.S. Patent No. 4,487,368 describes a sprinkler having a wobbling water distributor head mounted at the end of an angularly disposed tubular water-transporting arm. The base of the distributor head is mounted loosely between spaced shoulders. The wobbling motion of the head causes the distributor arm to traverse a circular path, so that a circular area is sprinkled. The present invention provides a means for con- trollaby varing the distance between the shoulders as the distributor arm rotates, whereby the dimensions of the area sprinkled are also controllably varied.