Standard 3/4" t-handle drain plug for use in the bilge drain holes in the bottom of the boat. This will work with the drain hole near the v-drive/transmission and the forward situated drain hole by the walk-through (not all models have both of these drains, some only had one of them while others had both).
There were also some older Malibus that used a 1/2" drain plug for these drains -- just make sure to measure the diameter of your drain hole if you are unsure.
This is not the magnetic drain plug used on some models with the drain plug sensors. It will fit in those models but the boat's sensor will not register it (it will show that the drain plug is not inserted).
This will not work for the transom drain in the back of the boat, which is a smaller 1/2" size plug.