These M55e cartridges are similar to the M447 yet a higher end cartridge according to Shure and their data specs.and limited quantities.

M55E Complete Specifications:

Tracking Force: 0.75 to 1.5 grams

Frequency Response: 20 to 20,000 Hz

Output Voltage: 6.2mV per channel at 5 cm/sec peak recorded velocity

Channel Separation: greater than 22dB at 1,000 Hz

Trackability at 1 gram force: 12 cm/sec at 400 Hz

Effective Stylus Tip Mass: 1.2 milligrams

Tip Radius: 0.2 x 0.7 mils

Inductance: 720 millihenries

DC Resistance: 630 ohms

Weight: 6.5 grams