local args = {
    [1] = game:GetService("ReplicatedStorage").ShopEntries.KnifeSkins["Bayonet Case"]
}

game:GetService("ReplicatedStorage").Interactions.Server.BuyShopItem:InvokeServer(unpack(args))
[[-- Change "Bayonet Case" to "Chroma Case, Elemental Case, Karambit Case, Dark Matter Case, Gold Trident Case, Honey Case, Seer Case, Sparkle Case]]