The racing slip leash/collar combo has a lobster claw clasp with locking mechanism. This is for fast on and off of the leash even if dogs have larger heads of are wearing muzzles. Most commonly used in Straight Racing, it also works great for FAST CAT and Lure Coursing. The Clasp itself adds about 2 extra inches so panel sizes MIGHT not be interchangeable with existing buckle/martingale collars of the same neck size. But with some heads up before ordering or ordering all at once. They can be made to interchange between the styles.
Leashes are 3/4in wide. This is a set width at this time.
Narrow Bases are 1.25in wide reduced to 3/4in by default. Narrow base with a border is 1.5in. Narrow base with padding is 1.5in. Narrow base with a border and padding in 1.75in wide.