When you need accurate control over rigging settings on performance yachts and non-marine applications, you can rely on Ronstan calibrated Sealoc turnbuckles. Engraved millimeter markings. Available as a complete turnbuckle for new installations or body only for replacement of non-calibrated bodies in existing rigging. Available in 1/4", 5/16" and 3/8" U.N.F. thread sizes to suit swage terminals for 1/8" to 7/32" and 4 & 5 mm wire. Ideally suited for "off the beach" catamarans, trailerable yachts and small keelboats such as E22's, J24's, Solings and Dragons Melges 24's Johnson 18's. So when it comes to accuracy, Ronstan calibrated turnbuckles have made their mark.