Serfas Thunderbolt USB Front Light The Serfas?« Thunderbolt (USL-6) provides high-performance and endless mounting options for a great price. If you?ÇÖre riding at night, let Serfas?« guide the way with our Thunderbolt (USL-6) Headlight. The 16-micro (double strength) LED strip puts out 90 lumens, giving you plenty of light to safely arrive at your destination. The USB-rechargeable Thunderbolt can be mounted virtually anywhere on the front of your bike?Çöfrom the handlebars to the fork. It?ÇÖs your ride, your call. Charge up, light up & get riding safely at night with the Serfas?« Thunderbolt.