These are new old stock record player styli commonly found in BSR ceramic cartridges, examples of which are X3H, X3M, X5H, X5M, SX-6M, SC-12M, SC-12H, etc. 
 
The ST12 can replace various other ST numbered styli. If you are unsure of which stylus you require, please email an image of your existing cartridge and stylus via the contact us section and we will do our best to confirm the if this is right for your player.
 
Supplied in plastic sealed bag.