Introducing Propel™ coverstock the next extension in Brunswick coverstock technology. Propel™ is a evolutionary coverstock developed by Brunswick to improve the midlane and backend traction of the ball on today's slicker oils and lane surfaces. The Propel coverstock was discovered through testing of new formulation additives and process changes in coverstock manufacturing. M.A.C.E.™Mechanical Asymmetric Core Engineering. The M.A.C.E.™ Medium RG core has three major benefits, Medium RG core system for a breakpoint further down lane, High RG differential to increase backend traction and High RG asymmetric differential to quicken the response time to friction. The Siege Defender II™ combines Propel Solid coverstock and the M.A.C.E.™ medium RG core to produce a ball motion that is clean through the front, consistent in the midlane with a quick response to friction on the backend. With its consistency from shot to shot and versatility across the lane, the Siege Defender II™ will be the first ball out of your bag and a new benchmark for Brunswick on medium to oily lane conditions. The Siege Defender II™ can be drilled using the standard drilling techniques developed for asymmetric bowling balls.