JSB Match Diabolo Exact King MKII Heavy .25 Cal, 33.95 Grains, Domed, 300ct .25 caliber 33.95 grains Round nose 300 pellets MkII pellet has a skirt diameter that is only 6.5mm, making the pellet work a little more reliably in some rotary magazines. Please note: The only difference between the original King Heavy and the King Heavy MkII pellets is the outer diameter of the skirt. This dimension on the original MKI pellets are 6.68 - 6.70 mm while the MKII pellets measure 6.58 - 6.60 mm. The appearance of the skirt or back of the pellet can vary.