Is there any adapters I should pick up? or anything that work nice with these sling? also what is the size that most like 1.25 or 1.5? since I have no way of checking my self.

Now the ? is should i get the CQB, SOP,or the CST sling from CQB I am leaning toward the CST, I am going to order one for my bushmaster standard A3 and my M4, My stepfather likes to shoot the M4 and he is righthanded but shoots left handed would a right handed sling mess thigs up for him? should I go with the sop for that gun since it is a left or right hand sling? and the CST for the standeard AR?

Personal preferences are based on a myriad of factors. The 1.5" wide straps distribute the rifle's weight over a breader area, which makes for greater comfort, but some find the greater width gets in the way. Single pt. slings make for easy transition to "weak-side" shooting, but also let the gun flop about. IMO these may be better suited to the shorter subgun class weapons, whereas 3 pts. seem to work better for carbines & above (M4 is in this latter territory). Again, this is a personal opinion, & is also subject to intended use.

Luckily for the consumer, several sling mfg's are competing for your dollars, so the benefit goes to quality. CQB Solutions 3-pt SOP sling has gotten a lot of good reviews. Tactical Tailor, Giles, Daniel Defense, etc., etc. all make good products, & have been featured here. Keep an open mind & even be willing to try a few for yourself. Experience & time may change your preference, too, so don't be surprosed if you get another brand down the road. I have a TT 3-point, & will be adding a CQB SOP sling to the mix.