Back shoulder press. shoulder-width or wide grip?

Can anyone tell me the difference between Back shoulder press, shoulder-width grip (behind the neck press), and back shoulder press, wide grip? Which part of the deltoid is used? (i also need good exercises for the back of my deltoid?) Thanks

I would not do behind the neck presses at all. Too many have suffered lasting injury from them.

And behind-the-neck presses are not particularly good for rear deltoid anyway. Rowing exercises are far better, for example Hammer Iso Row, Hammer Low Row, Hammer Row, bent rows (normal), and bent rows (Yates-style, leaning over only 20 or so degrees however, unlike Yates, pulling bar to about the navel instead of waistband).

There is also a Hammer Strength machine specifically for rear delts, a rear delt-fly kind of movement.

For me personally and many others, DB rear delt fly’s are not good mass builders for the rear delts. Perhaps because so little weight can be used. Moving 300 lb plus in a rowing exercise just does more than lifting relatively light DB’s.

The best exercise I have found for the rear delts are Pulls to the Face. You stand leaning back from a lat pulldown with a straight bar or rope and pull back to your nose kepping your elbows up and your arms parallel to the ground. Yo will feel these in your entire upper back,rear delts and traps