The middle spread is the distance between the two middle holes, center to center, on your receiver. The middle spreads on our Winchester 70 mounts are as follows: Winchester 70 Long Action: 3.805" This mount comes standard with a bevel on both sides making it ambidextrous. EGW recommends measuring the hole spacing in your receiver to confirm it matches with the dimensions they have published. Picatinny cross slots run the full length of the rail, which gives the shooter flexibility when mounting scope rings and other accessories. The channel in the center reduces the overall mass of the mount. Also, in many cases, it will not obstruct usage of factory iron sig Mfg: Egw