If you're not familar with hybrid stringing, it's simply using different string for the main and cross strings of your racquet. It's a popular technique on tour and is rapidly gaining popularity with players of all levels. Hybrids can be as simple as a thinner gauge in the cross strings (NXT 16 Mains, NXT 17 Crosses) to mixing natural gut and polyester like many pros. If you're thinking about trying polyester, using a non-poly in the cross strings can give you a bump in performance. If you're interested, select "Build a Custom Hybrid" in the string selection menu.