Ragim Matrix Limbs allow you to upgrade your bow to a heavier or longer bow. Matrix Limbs fit on Matrix Evo, Wildcat Plus, Matrix Custom, and Wildcat Custom Bows. Each Limb is rated for a particular size, if you have a 48" Bow, you need to stay with a 48" Limb. Some models may fit more than 1 size: a 66" Limb is a 66" limb on a Ragim #1 Matrix/Wildcat Riser, but it is a 62" on a Ragim #2 Riser. The same for a 68" Limb becomes a 64" when used on a #2 Riser. The Risers are as follows: #1 riser is used for 66", 68" 70", a #2 is used on 62" & 64", a #3 for 54" & 58", and a #5 is used for 48".