HEAD Synthetic Gut PPS 16 tennis string uses PowerStrip Technology to create a synthetic gut with more power than ever. PowerStrip (Polyphenylene Sulfide Strip) technology adds resilience creating extra speed on all strokes while the material provides heat and abrasion resistance, making it more durable than standard strings. Co-polymer center core. Multifilament wrap. Special pearl polyamide coating supports the durability of the string.