Hi Nicholas and welcome. No handgun specified (although you likely mean a Glock). FS = Fixed Sights. You can search the upc code to verify no front serrations. Cheers and stay safe!

Hi Nicholas, FS can mean 'fixed sights' or 'front serrations'. If you do not see front serrations in the picture, then it stands for 'fixed sights'.
Stay safe & have a great day!

Good evening to you!! Sorry but you didn't specify a specific firearm. FS means fixed sights. You can do a web search using the model number and UPC to see about what the serrations are and other specifications. Hope this helps. Have a good rest of your weekend.

With no firearm specified it makes it a bit difficult to answer properly. Yes, in Most cases "FS" = Fixed Sights. As James mentioned, use the UPC code when searching and you'll come up with the model & pictures associated with the UPC.