Mens Spike Vest S - Rabbit/Rabbit. The Spike is a lightweight, warm, and ultra-comfy synthetic insulated vest. This vest is Insulated with Pinneco Coreâ¢, which is designed to be more breathable, thermally efficient and sustainably engineered than other insulation options. The fit is relaxed, with a stylish slanted-quilt design which eliminates bulk and allows for layering underneath. All the while providing excellent range of motion.