Medium sized synthetic backpack.
The item id for Daypack Black in unturned is 200. You can use this ID with the commands below to spawn the item, give it to a player or buy it on a modded economy server.
Useable: Clothing
Size_X: 2
Size_Y: 2
Size_Z: 0.6
Width: 7
Height: 4
Blueprints: 2
Blueprint_0_Type: Apparel
Blueprint_0_Supply_0_ID: 200
Blueprint_0_Product: 66
Blueprint_0_Products: 4
Blueprint_0_Build: 32
Blueprint_1_Type: Repair
Blueprint_1_Supplies: 1
Blueprint_1_Supply_0_ID: 66
Blueprint_1_Supply_0_Amount: 4
Blueprint_1_Build: 32