Invader Cocksheath Black Ice from Oxballs. Oxballs invented the modern cocksheath by morphing our original cocksling to a sheath creating the first sheath that really stay on no matter how hard you play. Invader is that good and more, our first open ended sheath with wavy ripples on the shaft, and texture inside, So everyone gets max stimulation. Made of Plus Silicone, our slick soft Silicone and stretchy Thermoplastic Rubber TPR blend.