The mid model contains an extra 3" and 4" bolt. The extra 4" bolt allows a 1" wider stack for 10~15 more pounds on the high end. On the low end, the extra 3" bolts lets you use the more versatile two-bolt setup down to a stack width of 6" (3"+3") while the base model has a minimum of 7" (3"+4").
Our kettlestack adjustable kettlebell handle provides a wide variety of convenient fast kettlebell workouts. Each Base option Kettlestack holds up to 70 lbs and includes:
hard tempered support bands
one 3" bolt
one 4" bolt
allen key
hard tempered 4.25" support axle
(weight plates (and the big shipping charges) are not included)