Return / Recoil Spring for the FN SCAR 17. This is not an original FN part, but an after-market reproduction made to the same dimensions.
Springs have a life of between 8,000 and 10,000 rounds before they start losing their strength, so if you shoot your SCAR a lot, you will eventually want to replace the main spring for most reliable operation. Good news is it is very easy and fast.
F184430010 is the part number from FN.
Product images show one OEM spring, and one ShootingSight spring – you cannot tell the difference.