1. Do you have a K/L/X (Medium) Frame Revolver?
From the way the grips look and feel, K/L and N frames are very close in size and fit. The N frame is more solidly built elsewhere for magnum calibers. Therefore, the larger magnum calibers are generally N Frame. The best way tell the difference between K and N is the model numbers.
K Frame Model numbers: 10 to 19, 547, 586, 581, 617, 686, 696, 986, 55, 64, 67, 48
N Frame Model numbers: 23, 25, 27, 28, 29, 625, 629, 627, 327, 325, 329, M&P R8, 57, 59, 624, 625, 626, 627, 629, Magna Classic
K, L and X frames are the same as far as grips are concerned.
2. Do you have a Round Butt Frame?
Understanding Conversion Grips
A Conversion grip changes a Round Butt Frame grip to look and feel like a Square Butt Frame grip. It extends support at the heel of the hand for additional control and recoil absorption. A Round Butt Conversion grip will not fit a Square Butt frame and a Square Butt grip leaves a huge gap on a Round Butt Revolver.
The Smith and Wesson K-Frame revolver family are the iconic American double action revolvers. The first K-Frame was introduced in 1899 and came, from the beginning, in both round butt and square butt configurations. These revolvers were used in both World Wars and were particularly popular with the English in World War II, where Smith produced 568,204 revolvers for the British armed forces. While there have been many changes in the mechanism or models, Smith has been careful to maintain frame consistency--and grip interchangeability. From the beginning, most of the K-frame revolvers were square frames. Today, most of the K frames produced are round butts. (For a superb, detailed history of Smith revolvers--and more--go to Roy Jinks, History of Smith and Wesson. Find it. You'll like it.)