I bought this to replace a Garmin soft strap that was getting unreliable after 2 years use, after reading in several places that it was compatible.
Not only is it compatible, it performs better than the Garmin strap and is more comfortable, at about a third of the price.
This has longer electrodes than the Garmin strap, which seem to be made out of conductive rubber rather than the harder plasticky electrodes of the Garmin, and they are more flexible. Because they are more flexible the electrodes mould to your body better, making them comfortable and allowing them to get better contact.
The Garmin sensor just clips straight on without any problems.
A great investment