Snap Together Female. Furniture Grade. Glues into a 1" Sch 40 pipe (furniture or plumbing, not thinwall and not class 200). Provides Snap Together Female to snap in a Snap Together Male. The "Snap Together" fittings are unique. They are the only ones that combine two different sizes of fittings. Normally you'd connect a 3/4" pipe to 3/4" fittings. However, the Snap Together fittings allow you to combine a 1" pipe to a 3/4" fitting. The reason you would do this is to get a smooth "same size" finished product that you can easily take apart and put back together. Such as you see here:
Note: These work better with plumbing grade fittings because they have a distinct flat edge that mates up with the pipe. Furniture grade fittings usually have a bevel at the end, so they look weird. In the picture above that's a plumbing grade cross with plumbing grade pipe.