Hmmm i am confused, i have an X arm which looks exactly like that, but i heard the back bracket needs to have an extra hole for am4 which mine doesn't have. Or is the AM4 X arm just longer? or shorter? whats the difference, i have one that fits on an LGA 1151 motherboard, ill give u an image of my back bracket https://i.imgur.com/WDTQubx.png