Sorry for another dumb question but I'm not sure and this is my only reliable place to turn. I have a S&W M&P 15 optics ready which has no iron sights just a pic rail on the flat top and the front gas block. I purchased front and rear flip sight and a rear carry handle. I can't get the sights even close to dialed in My question is are there different flip sights for a gas block mounted vs a front rail mounted ( height difference) A guy at a local show was telling me they were different. I got my sights from the dealer where I purchased my ar thinking he would know what to sell me.