the inserts vary in what they weigh between different brands of arrows...you generaly add 15 to 20 grains to the tip...you can counter that by dropping weight in your field point or broadhead...if you are a target shooter and use glue in tips,you can get them in just about any weight you want without adding any weight.these are easy to set up and if you plan it out,you can have the arrow at the same weight you currently shooting.you do have to cut the arrows to specific lengths to make it work...no big deal,you have to cut new arrows anyways.with the set up i have now,i have a 10%foc...these are the most consistant rest that i have ever used....no moving parts,no noise when released(none),no wiskers to freeze when it gets wet,no cords to break or come loose...the magnets are rare earth magnets that will last longer than you will live and there are some new concepts with this rest that are in development right now...if anyone buys one or has one and needs help on setting it up,just give me an pm and i will gladly help.