Easykeeper, yes the risers are different lengths; giving each a different size sight window. The PMA has a 18" riser, PSA has a 16" riser, and the PCH has a 14" riser. Because of this the limbs are not interchangable between models. Black Widow has recomendations for your draw length, you can choose a longer bow for slightly more comfort in shooting. Or a shorter bow for ease of manuverability. I can't recomend an all around BW, as they are great bows. I'm curently shooting a 56" SAX. Just love this bow. They do have a test drive program. Hope this helps.