New. Came packaged with a Garmin watch I purchased.

This model is the middle generation of Garmin's heart rate sensors. It has advantages over both its predecessor and successor. The first gen. Garmin HRM was the "hard strap" that had a large 12" plastic sensor area that fit across your chest; it connected with a soft elastic strap. This 2nd gen. Garmin HRM is the "soft strap" version with much less plastic (more comfortable) and with a removable sensor module that allowed for strap washing as well as strap replacement. Garmin's new HRM with running sensors is a similar soft strap but the sensor isn't removable so you can't replace the chest strap should it wear out.

Uses ANT+ communication technology. So it works with Garmin fitness products and other brands that use ANT+. This even includes many Samsung Galaxy phones as Samsung embedded many of their phones with ANT+ hardware.

The strap is made of a comfortable soft fabric. Pair it with your compatible device just once, and it will automatically recognize it each time. Optimized for use in crowded areas like the gym and road races, it won’t pick up any signals but your own. The heart-rate module is removable from the strap so you can wash the strap as often as needed.

Strap Length: Adjustable from 21" to 29.5"

Water Resistance: 30 meters

Battery: User-replaceable size CR2032 (3 volts)

Battery Life: 4.5 years (based on average use of 1 hour per day)

The product manual can be viewed/downloaded here:
https://support.garmin.com/support/manuals/manuals.faces?partNo=010-10997-02