Eurotool Cool Cup For Soldering & Jewelry Repair. This is a new Eurotool cool cup. This is used when soldering and resizing rings. Perfect for jewelers and crafters. Just fill the cup with cold water and submerge the stone and mounting while soldering the shank to keep the stone cool. Soldering cup includes special locking tweezers designed to slip on and off the post. It measures approximately 3 5/8" (91 mm) in diameter and 1 3/4" (44 mm) deep.