Excellent for mainsheet systems, Schaefer swivel cam bases allow easy cleating from almost any angle. Our smallest stainless arm swivel base is ideal for dinghies or daysailors and contains our small sure grip cam, mounted eye strap, and plastic bullseye. - Our larger aluminum arm swivels accept either 5 or 7 Series blocks with a heavy-duty spring and bucket adapter to support the block in an upright position. These high strength arms are optimally angled for easy hand adjustment, and include our durable Sure Grip cam cleat with mounted eye strap.