BudsGunShop.com - Compensated FS

Hi Angel, Compensated - The slide is compensated, has a ported barrel and slide (not seen in picture)
FS - Fixed Sights
You can see compensated slide/barrel here (3rd Picture down) >>> gunauction.com/buy/12725158
Stay safe & have a great day!

FS= Full Size.
All sights on Glocks are Fixed with the exception of the Glock 44 in .22lr which has an adjustable rear site for windage.
The barrel and slide are ported (Holes cut into both) to expel gasses making for much more manageable recoil.

Hi Angel and welcome. FS = Fixed Sights and Compensated - Ports in the barrel and slide (slots behind the front sight) top as pictured here : guns.com/firearms/handguns/semi-auto/glock-g20c-10mm-striker-15-rounds-4-6-barrel-new?p=1068884&soldout=1