One pair of earring backs.  I've had multiple repeat customers ask for these for their other earrings after they've used these, so I'm now offering them to you! 
 
For post earrings.
 
Compared to regular butterfly backs:
More secure, plus you can push them as far up the post as you want to get that perfect fit without relying on where the notch is
Much more comfortable!  No pinching or sharp edges
Don't go sideways when you're putting them on
Easier to put on and take off since there's more to grab ahold of
Nap approved. Since they cover most or all of the post, there's nothing stabbing you in the neck.  Side sleepers may wind up with tighter earrings if you press on them just so, but otherwise they're very comfy.
 
Silicone covered sterling silver butterfly backs.  These are the large size (6.3mm)  The silicone completely covers the silver, and people with sterling allergies are fine with them.  Unfortunately they're not available in argentium, but it doesn't seem to matter with these since they're sealed up. 
 
All butterfly backs can get looser with time.  But it only takes a second to tighten them back up.
The post is actually held in place with the wings, not the hole!
With the backs off the earrings, find the wings (curly bits of metal)
With a finger and your thumb, squeeze the wings towards eachother. 
It doesn't take much, just a quick medium firm squeeze and you're done!  Now your butterfly backs will have more tension on them.  You can do these with the regular (all metal) styles too.