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 stronger and more corrosively resistant grades such as Bumax 88 (Class 80), Bumax 109 (Class 100), Bumax DX129 (2205 - Class 120), Bumax SDX109 (2507 - Class 100) and 2507 (Class 80). The following is an approximate guideline.

Stainless Grades	PREN Values	Features/Benefits	Useful For	In Action
410	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	12	A nickel-free grade with high carbon It is stronger than 410	Spring pins in less corrosive environments
HARDTEC	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	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	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.
LEAN DUPLEX 2202	25	Combines ferritic and austenitic structures for high strength and corrosion resistance Excellent fatigue resistance — 3x greater than 304 Performs better than 304 in acidic environments	Infrastructure projects, machinery, and chemical processing Applications requiring high strength and corrosion resistance at a lower cost
BUMAX DX 129	34	The world's strongest stainless steel bolt Highest strength - unlike high-strength carbon steel fasteners, DX 129 does not suffer from hydrogen embrittlement Excellent fatigue resistance — 3x greater than 304 Lower thermal expansion making it more dimensionally stable in temperature variations	Versatile applications in defense, marine, aerospace, automotive, manufacturing, and construction
DUPLEX 2205	34	Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking Higher strength than austenitic grades like 304 and 316 Good weldability and toughness Suitable for harsh environments including marine and chemical processing	Coastal and industrial applications Marine hardware, structural components, and pressure vessels
2507	41	Super Duplex Stainless Steel High corrosion resistance Fully resistant to localised corrosion (pitting/crevice corrosion) when immersed in seawater	Fully resistant to localised corrosion (pitting/crevice corrosion) when immersed in seawater
Bumax SDX 109	41	Super Duplex Stainless Steel High strength and high corrosion resistance Situations requiring high strength and very high corrosion resistance such as constant salt water immersion	Situations with very high corrosion resistance such as constant salt water immersion
1.4529	47	Outstanding resistance to chloride-induced corrosion (pitting, crevice, and stress corrosion cracking) Performs well in seawater, chemical processing, and acidic environments	For use above indoor swimming pools, chemical and petrochemical processing, power generation

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 New Zealand's's harsh conditions - especially coastal environments.