Is it legal in HC,AHC,and MBR to use pins with different diameter fiber optic? Ex. 20yd pin .019 30yd pin .019, 40yd pin .010, 50yd pin .010. I read the rules and a believe the rules applying to the circle pins are the style that are open circles. I would like to know if different size fiber opticsare legal. Thank you.

You can use any solid pin size you like.

You can use any size pin you like. They dont have to all be the same diameter, you can go with different sizes for different yardages if you want, its not illegal for IBO rules.