All the needles are triangular, therefore they have three edges. The ULTRA needles have one single small barb per edge (three barbs total), with the barb approximately 1/8″ from the tip of the needle. The Regular needles have two barbs per edge (six barbs total), and they are at staggered depths from the tip. For rooting into vinyl (or a silicone/vinyl mix), a 38 gauge ULTRA needle roots about as finely as a 42 gauge regular needle (remember, the bigger the gauge number, the smaller the needle). This is because our ULTRA needles pull fewer hairs per folicle.