Sparkrite Self-Assembly Black HT Lead Set. Sku: LSC4 & LSCPlus2 - Sparkrite 'Self Assembly' 6 Cylinder HT Lead Set - 7mm Double-Silicone. Sparkrite 'Self-Assembly' HT Lead Set. Our HT leads use double silicone insulation surrounding a carbon ferroflex core for maximum spark transfer and electrical suppression, and minimal power loss.