Knock-off products may look like SealtightTM, but only SealtightTM Fasteners offer the quality and precision required to create the perfect sealing solution. Other companies claim that their screw products will seal, but they don't care what the groove dimensions are as long as they use an O' ring that is larger than the volume of the groove. Unfortunately, when an O' ring is too large for a groove, it causes what is known as compression set. When an O'ring has gone "compression set" its sealing capabilities are disrupted and unstable. SealtightTM is the choice of industry leaders and has been for decades.