WD-40 Multi-Use Product was invented in 1953 with five basic functions: It lubricates, penetrates, protects, cleans and removes, and displaces moisture. WD-40 Specialist Fast Release Penetrant is specifically formulated to penetrate rusted and corroded parts and loosen seized fixings. To determine the penetrating ability of a fluid, a large nail is used to evaluate how quickly and completely the fluid will move up a vertical surface. This is referred to as a Nail Climb Test and according to this test, WD-40 Specialist Fast Release Penetrant penetrates at least 50% faster and farther than WD-40® Multi-Use Product. WD-4 Multi-Use Product has over 2000+ fantastic uses and is a great multi-use product, but for a specific application, such as penetration, we recommend using the WD-40 Specialist Fast Release Penetrant.