The Plate-Loaded Lever Curl Dumbbell is very nice as a single bar. I listened to one reviewer and bought two. I connected them together with a 5/8” fully threaded 48” long rod and technically it is no longer a dumbbell. I shackle the dual Plate-Loaded Lever Curl Bars to the two carabineers at the ends of this dually on my X-3 rack and it is ready for use. I am happy with the single Plate-Loaded Lever Curl Dumbbell however two is even better. This connection uses 8 nuts, 28 washers (various), 4 lock washers, and 5/8” fully threaded 48” long rod, 2 carabineers, three 1ft stainless rods with inner diameters of 5/8", and three 1ft stainless rods with inner diameters of 3/4". The stainless steel rods are implemented over each other for strength. The only trick is to use washers large enough that the carabineers at ends of the dually are sandwiched and can't come loose. These can be connected with a 5/8” fully threaded bar 18” to 24”, if one does not want to shackle or store this 48” version. I am very happy with my purchase of two Plate-Loaded Lever Curl Dumbbells.