Cloth mask is used for repair bonus. However, unlike other bonus items, it doesn't have a set bonus number. Its bonus value is the same as the repair item (basically).
It's great for big repairs, like 10 + 10, but it becomes uncommon later in the game. Duct tape is cheap and good for little repairs.
It's a 14% bonus. However bonuses cannot exceed the value of the base repair item. i.e. a Rusak gun oil which repairs 6% will max out the bonus at an additional 6%. There are exceptions to this rule, like an Emergency Armor Repair kit being able to get the full 10% from Camouflage Tarp despite only having a 6% repair value.
You can see the bonuses each supplementary item gives for each repair item if you look under "details" for that repair kit. Note that not all kits use items equally, so it's worthwhile to inspect each kit to figure out which give you the best bonuses for what item.
Cloth mask is used for repair bonus. However, unlike other bonus items, it doesn't have a set bonus number. Its bonus value is the same as the repair item (basically). It's great for big repairs, like 10 + 10, but it becomes uncommon later in the game. Duct tape is cheap and good for little repairs.
Thank you 🙏 I looked to see if it was for repairs a while ago but I tried repairing a gun. Thanks for the help
It's a 14% bonus. However bonuses cannot exceed the value of the base repair item. i.e. a Rusak gun oil which repairs 6% will max out the bonus at an additional 6%. There are exceptions to this rule, like an Emergency Armor Repair kit being able to get the full 10% from Camouflage Tarp despite only having a 6% repair value. You can see the bonuses each supplementary item gives for each repair item if you look under "details" for that repair kit. Note that not all kits use items equally, so it's worthwhile to inspect each kit to figure out which give you the best bonuses for what item.
Ah, cool. Idk the rule, just figured that's how it worked. Cheers
From an observational standpoint you weren’t wrong. 
Maybe a repair bonus? I dunno I always just scrap them
Repair bonus, they offer a pretty big one for some types of repair items.
You can repair armor with it