Promise Thunderbolt SSD Storage Devices
Promise Technology was the very first manufacturer to even offer a ThunderBolt storage device when Intel and Apple first introduced the interface. Sadly, they deliver high-end enterprise solutions with multi-drive hard disk based RAID arrays that begin at 1 thousand dollars and up. They offer original, 20Gbps Thunderbolt 2, and 40 Gbps Thunderbolt 3 hard drive raid array solutions to high-end markets.
They do sell standalone Thunderbolt drive enclosures, though you'd need 3.5" to 2.5" adapters to custom build a RAID with matched off-the-shelf SATA III SSD's of your choosing.
Promise Single-Drive ThunderBolt Backup Drives
As a company Promise really isn't into the consumer hardware space at all. They're strictly a high-end, high-performance company catering to the most demanding data storage and transfer markets who are far more likely to use rack-mount arrays for businesses and Audio / Video editing studios than anything for the consumer space.
Promise Multi-Drive Desktop ThunderBolt RAID Backup Drives
The Pegasus line starts with a quad drive hardware RAID enclosure using 3.5" HDD drives and goes up from there. They've been on the leading-edge since ThunderBolt's inception: First with 10Gbps original ThunderBolt, then updated quickly to 20Gbps ThunderBolt 2. They're now offering 40Gbps Type-C ThunderBolt 3 RAID arrays for the most demanding environments.