You can purchase wieght tubes for the carbon express CX arrows they come in 2gr per inch and 3gr per inch They cost around $10-$15 a dozen I payed $9.99 for each at eagle archery. I ordered both the other day and when they come in I am going to take 3 arrows to the bowshop and shot one arrow standard and the other two with the different weight tubes installed juist to see which gives me the most KE and momentum combination. I have to say my Allegaince is shooting awesome right now that bow feels like it was made for me and I have bought several different bows over the past 3 or 4 years and have on had only two other bows that have felt this way a Reflex xpress solo cam and a Pro38 dual cam.