Mystery Ranch Endurance Yoke, sold separately from the Bridger pack, allows for a more comfortable, larger coverage strap set up. The Mystery Ranch Yoke in conjunction with the waist belt is how you customize the fit of a Mystery ranch backpack. The pack and frame stay the same size but by swapping out and adjusting the waist belt and yoke to your body you can get a custom fit. Make sure to reference the Mystery Ranch sizing chart for both torso length and waist size. You may need to buy both a yoke and waist belt to get the fit perfect.