36g 3b = 36 gauge crown rooting needle with 3 barbs. A larger gauge needle for beginners and for firmer vinyl heads. (the larger the gauge number the smaller the hole produced when inserting the needle)
42g 3b = gauge crown rooting needle with 3 barbs. A smaller gauge needle for rooting and smaller holes.
10 needles per pack.
Click on the illustration to see how barbs help you when rooting the hair. All tip photos are magnified to show shape of the end. You can not really see these shapes with the naked eye very well.
Crown needles are good for their high dimensional accuracy of the barbs which will gather more than one fiber at a time for greater/faster rooting.