A2 front sight

Re: A2 front sight

The shelf that contains the front sight post is about .04" higher in a F marked front sight base. This allows for a little more elevation adjustment before the front sight post is pushed above the protective "wings".
 
Re: A2 front sight

The "F" marked front sight assemblies are for flat top upper receivers. Going rate on them is about $25 stripped regardless of type, unless it's a Colt as they're always a bit more.

Are you looking to sell or buy? If you're wanting to buy, then provide a bit more information to your application.