The best upgrade I know of for any bridge with USA spacing. (Your strings must be at least 2 3/16" e-to-e spacing- That is ALL USA Strats, Japanese Strats, most high end American and Japanese imports)
You get six beautifully cast aluminum bridge saddles with hardened steel roller bearings, complete with screws, springs, hardened steel height adjustment screw- all ready to assemble. These things work really well, sound excellent, and virtually eliminate string breaking at the saddle. Yes- tuning stability is drastically improved as well- combine this with a well cut nut and now you can whammy IN TUNE!
These are spaced to fit USA spacing, so if you have 2 1/8" or narrower string pitch they will not fit.
When replacing the pot metal saddles on a typical Asian guitar you'll immediately notice the big ballsy tone, the tremendous string response and the great tuning stability.
There's no cheaper way to breath some TONE into your guitar. These also work on Tele humbucker bridges and Strat hardtail bridges- if your saddle has a center mounted screw and the strings go through the body- these will fit!