The MP-500 is the top model in Nagaoka's line of moving-permalloy cartridges. It retailed for $699 US when introduced in 2013. The MP-500 replaced the MP-50, and received excellent reviews. It competed with Ortofon's 2M Black, and comparably-priced models from Grado, Audio-Technica and Clearaudio. It features the boron cantilever and line-contact stylus, and overall appears very similar to the outgoing MP-50. The MP-500 also has a replaceable stylus, which is secured by a set-screw.

Specifications:
- Type: Moving magnet
- Cantilever: High-strength boron
- Stylus type: Superfine line contact diamond
- Output voltage @ 1kHz,5cm/sec: 3mV
- Frequency response: 20Hz-25kHz
- Channel balance @ 1kHz: > 1dB
- Channel separation @ 1kHz: > 27dB
- Recommended loading: 47k ohms
- Dynamic compliance: 8.5 x 10-6 cm/dyne
- Tracking force range: 1.3 - 1.8 g
- Weight: 8 g
- Break-in period: 30 hours
- Stylus replacement: Nagaoka JN-P500

Reviews:

http://wallofsound.ca/audioreviews/review-the-formidable-nagaoka-mp-500-phono-cartridge/