Series 45 Stand-Up Core Block - SwivelingCore Blocks™ are a true all round solution. A tuned 2-stage bearing system provides excellent performance across the full working load range with an integrated thrust bearing feature and the resilience to handle high dynamic or static loads. Acetal sheave, alloy cheeks and stainless fixings complete the durable package. For reliability and a long service life, these blocks are the right choice for sheets, halyards and control line applications for cruising and racing.Universal BearingDynamic and high static load performanceThe Ronstan Universal Bearing incorporates our proven 2-stage bearing systemStage 1 - Under moderate loads, Acetal ball bearings ensure minimum frictionStage 2 - Under heavy loads, where deformation of ball bearings alone would result in increased friction, a sliding Acetal bearing on a polished stainless steel race takes over, maintaining low friction performanceAdditionally the ball bearings are configured to act as a thrust bearing between the sheave and cheeks, preventing the sheave from rubbing on the cheeks and causing friction when the line lead in and out of the block isn’t perfect. Particularly important for cheek blocksAlloy Cheek PlatesBlock cheeks are manufactured from the highest quality alloy for maximum strength. Material optimization and the cut-away design minimizes weight and allows easy fresh water rinsing of salt and debris from the bearings.  Cheek design has been further styled with flaring at the block throat and reduced gap between the cheek and sheave, minimizing rope wear.Features:High dynamic and static load capacityEfficient 2-stage bearing systemBall bearings to counteract side thrust loadsClass leading performance and sleek, contemporary stylingDurable aluminium alloy cheek platesCentral hub hole can be used as a becket take-off or tie-up pointFeatures a strong cast padeye base with a swivel head post to allow full rotation and articulationApplications:Ideal for mainsheet, halyard and spinnaker sheet applications on boats to 10M (33')Various control line applications on larger yachtsAlloy sheave models are available for use with wireMaterials:Sheave: U.V. stabilised AcetalCheek body: Aluminium AlloyBall Bearings: High compression strength carbon black AcetalShackle, head post & hub: Grade 316 stainless steel