I'm looking for sights and noticed they have the same magpul mag248-blk rear sights at different warehouses for different prices. Anyone know why? Rear sights are $59.97 at one and $45.14 at the other, same with the fronts $39.97 and $31.10. I also found them at Outdoorgearbarn.com. Any feedback on either site would be good. Also has anyone used the Magpul sights above with the mag247-blk front or the arms #71lf-r?