Haven't had a chance to use all but will say, there is some variance in the type of bearings inside and some have more grease from factory than others. Although it's very easy to open up and ensure proper amount of grease to the rails and balls. For those interested or concerned. My use is to utilize the wheels by themselves as replacements in different situation. The hole size for the wheels are 3/8\", bolt and nut size is 14mm.