All attachments are for rifle-type weapons, unless otherwise stated. You can also click the name of an attachment to equip it. To cycle through the attachment options listed for each slow, press the key that corresponds to the slot number. Press or select the weapon info for from Nanosuit display to open this menu. The degree of modification available varies from weapon to weapon and the SCAR rifle is a highly customizable choice.
Your kit includes basics such as silencers and interchangeable sights, but weapons obtained during your mission can yield a range of attachments to give you more choice. Modify your weapons with a range of attachments to deal with whatever enemies you encounter.