What's a good cartridge for infinity black widow?

Shure V15 was made for that tonearm. My friend has that combination and it sounds great

Mr J- Which V15? The V15 series began in 1964, and there have been a plethora of variations since, with many differing compliances.

Rodman is right, not only is the widow ridiculously low mass,it is also a double knife edge bearing (like the early SMEs).These were once thought to "chatter" if too low a compliance cartridge is used.Most moving coils would be out of the question! Over the years I found the Shures (type III or newer),ADC XLM,Sonus Blue,Empire 2000 EII, B+Os,and AKG P8 all suitable. This was when the industry was on a "low mass" kick.BTW,you will notice that there are almost no arms available today that are this low mass.You might be better served to look for a used MMT or Audioquest PT,that way you would have more cartrige choices. These are usually available at a pretty reasonable price.The BP works well with the MMT.

Get a grado wood body.Ive read there good for light arms.A guy on another sight swears by them with his sme series III.If it works on that set up it will work on yours too.

I once owned the BWidow mounted on a Denon and had good results with Sonus Blue, and high output Denon moving coil. It may be a low mass arm, but sounded great.