I've only come across this recently, and the release date is still unknown. But it's definately a welcome surprise to those fans of the old logitech mx300 mice. It's design looks to be identical to the mx300, with the inside of a 2000 dpi laser engine, defaulting at a refresh rate of 500 Hz. There doesn't seem to be any adjustable weights, but other than that it has all the features you already see in past logitech gaming mice.

Source: Logitech