There are many different grades of Stainless Steel. The most common are 304 and 316. Some fasteners are also made in 303, 410, 420 and 430 as well as more corrosively resistant grades such as Bumax (2343) and 2205. The following is an approximate guideline.

Stainless Grades	PREN Values	Features/Benefits	Useful For	In Action
410 SS	11	A Martensitic grade that can be hardened by heat treatment	Self-drilling (into metal) screws in non-coastal and less corrosive environments (e.g. interior use)
420 SS	12	A nickel-free grade with high carbon It is stronger than 410	Spring pins in less corrosive environments
HARDTEC SS	16	A Martensitic alloy like 410 so can be hardened with heat treatment Has Molybdenum added so offers much better corrosion resistance (similar to 304 grade)	Self-drilling (into metal) screws.
304 SS	19	A general purpose grade It is commonly used because it offers reasonable corrosion resistance, and is reasonably priced.	A variety of applications, including interior and non-coastal exterior applications which are hidden from sight (as it may tea-stain)
316 SS	24	Good corrosion resistance Needs fresh water/rainfall to wash off contaminants like sea salt to maintain surface corrosion resistance and avoid "tea-staining".	For exterior applications, including near the coast with the correct surface finish and proper maintenance. Good material for handrails, downpipes and building fasteners.
BUMAX 88 & 109	25	A 316 grade with extra Molybdenum added Usually made to high strength classes 80 and 100 Has excellent corrosion resistance	Where high strength and excellent corrosion resistance is required.
2507 SS	41	Super Duplex Stainless Steel High strength Fully resistant to localised corrosion (pitting/crevice corrosion) when immersed in seawater	Situations requiring high strength and very high corrosion resistance such as constant salt water immersion

WARNING! BEWARE OF LOW NICKEL STAINLESS STEEL Some proprietary grades with high manganese and low nickel have found their way onto the market and are being sold as 304 or 316. Some are even stamped as such. These alloys also have low chromium and are not suitable for Australia's harsh conditions - especially coastal environments.