SpinLockBuddy™ is an accessory attachment to threaded dumbbells and barbells that is mounted over the "Spinlock" nut that secures the weights. 
While being a secure option on barbells and dumbells, spinlock nuts are not exactly fast, comfortable or easy to tighten. SpinLockBuddy solves these drawbacks by providing a comfortable but firm grip that makes it much easier to apply force when tightening. Being a larger diameter it adds rotational momentum and is significantly faster to mount and dismount by throwing a rapid spin on the nut. Who knew that slapping nuts could be fun?

SpinLockBuddy™ comes in two primary flavors.

The large triangular and winged  22cm-Ø is built for barbells with larger disks.

The smaller circular and ribbed 10cmØ is built for dumbbels with smaller disks.

Both are compatible with 25, 27 and 30mm barbells, but these grips are not designed to routinely handle the full weight of a loaded barbell and should only be used with weight disks larger than the grip. 

Spinlocks are usually cast iron made by several manufacturers, while we try to ensure a universal fit, if you are unsure about the sizing there are two key dimensions to look at. The total outer diameter tip to tip is max 71mm, the protruding cylindrical section that holds the rubber gasket is max 48mm. If your spinlock nut is equal or less than this we are pretty sure it will fit. 

SpinLockBuddy™ comes with the lid mounted to ensure a proper fit.
Unscrew the lid and place your spinlock nut into its new home with the flat side down. Test the fit by gently screwing the lid on, put the lid flat against the threads and rotate slowly counterclockwise until you hear and feel a small "click", this is where threads start and will engage when rotated clockwise. No force should be necessary, if there is significant resistance it has most likely not properly aligned the threads and applying force can damage the threads. If it will not screw on when gently rotated, try unscrewing counterclockwise and realign. 

With the lid screwed on, look over and check if the fit is good and the protruding contact area of the nut fits into and is higher than the lid.

While the SpinLockBuddy™ will function like this, it is designed to be secured in place by caulking the gap between the slanted "stars" on the nut and the grip cavity around it. The nuts are usually cast iron and not produced to any specific tolerances, the exact size and slant of the "stars" vary significantly and this was the only reliable and easy way to ensure a solid fit on the vast majority of spinlock nuts.
We highly recommend properly mounting it this way to get the best durability and function out of your new SpinLockBuddy, omitting this part may result in premature failure if stressed. 

Almost any caulking or glue will work fine, the intention is to lock it in place and remove any wiggle room, providing a solid fit all around. 
Acrylic caulk is probably the easiest to work with, epoxy glue works fine and "hot-snot" gluegun will work in a pinch. Silicone or very soft and squishy material is not optimal but better than nothing. 

If you dont own a caulking gun, you should probably just buy one or ask an adult if you can borrow theirs. Not everyone needs to own a firearm, but every modern household needs a caulking gun. 

You can apply caulk around the entire edge after removing the lid, or just push a healthy dose into the two holes on each "star" to provide a good fit. The goal is to fill the cavity between the two slanted surfaces with good contact on both sides, avoid just applying a thin bead on the top as this may be insufficient support.
Optionally, put a small dab of caulk or glue on the left side of the threaded sections, this will ensure a strong and permanent fit for the lid. 
There are slots designed to catch superfluous caulk, but if you got a little too enthusiastic with the caulk it should be cleaned up before it hardens.

Gently remount the lid, once it makes contact with the nut below you can apply more force to properly tighten it. There are 4 slits for using coins or the handle of a teaspoon to get some extra grip if necessary. No more than hand applied force is necessary, going overboard could potentially damage the threads. 
Make sure the nut is properly centered i the hole. We recommend letting the caulk harden before being put to use.