This listing for an Mayumi V4 Modchip for the Playstation 1 (Psone, PS1, PSX)
When installed properly, These chips will allow for Region Free Disc playback as well as Backup support.
This modchip is a 8 wire install and will work on any Ps1 revision except for the early models with the Av Jacks (Pu-7 / Pu-8)
The Mayumi is an 8 wire install and in my experience works much better than the MM3 for every console that supports it.
Keep in mind that Pal games will likely have display issues to the 50htz to 60htz differences.
These chips are programmed to work on North American consoles (NTSC-U) if you have a Pal or NTSC-J console, this will not work for you.
Chip comes with some 30 AWG hookup wire as well as a ModzvilleUSA approved vinyl sticker.
For install Diagrams I'd recommend checking out Quade's Page Here!