Sensei 77-72mm Step-Down Ring

That is a step down ring. If your lens has a 77mm filter thread it will fit and allow you to use 72mm filters on it. Note that stepping down you will get vignette.

According to our shipping specifications, the product will weigh .30 lb.

This ring is to attach a 62mm filter to a 77mm lens thread but for wide lenses, that's a no-no, vignetting will occur.

No. The 58mm side is male and screws into the lens. The 49mm side is female and receives the filter's male threads.

The Sensei 52-48mm Step-Down Ring has female 48mm threads on the front of the ring to allow you to connect a filter with 48mm male threads to the step-down ring. The back of the step-down ring has 52mm male filter threads which will screw into the 52mm female filter threads on the front of your lens.

I am using this step with a Canon EFS 10-22mm. At 10mm there is minor vignetting only in the extreme corners, but it is barely noticeable. When I zoom out to 11mm and beyond, the vignetting goes away completely. I typically post process my macro shotsand crop closer to the subject. I have never noticed the vignetting until you asked this question. I had to setup a shot and test it to give you an accurate answer. In my opinion, the product is 100% acceptable.

Yes.

Yes you use more than one step down adapter ring. Note you will get a lot of vignette when using that setup of 77 lens filter thread to a 49mm filter.