Not sure if anyone has ever posted a pic of the lifters and see lots of confusion about these, so here is what they look like. The first pic is a conventional Hemi lifter. The second is a an MDS lifter. They are dimensionally identical. The hole in the side where you can see the pin is what makes them work. This lifter beat out the trunion bearing which let it bounce and destroy the internal body, which is why the pin is turned. Normally the pin sticks through the hole and locks the lifter halves together, making it a conventional lifter. When oil pressure is applied from the solenoid (MDS mode activated), the pin is pushed in, and the internal body can collapse enough to prevent valve lift, but not enough for the pushrod to loose tension to the rocker.