POWRKOILâ„¢ 18 COVERSTOCK: PowrKoil 18 coverstock is a proven performer in the bowling industry. Aggressive in the oil and strong off the dry, PowrKoil 18 is a perennial favorite among all styles of bowlers. The Karma Blue / Green Pearl uses a pearlized version of PowrKoil 18 which provides more mid lane traction for a […]