This type of wolf suppressor is known as the Wolftoter (a/k/a Wolfton) and is available for three ranges: Low D-E (yellow tab), Medium Eb-F (green tab), and High E-F# (blue tab).   Installation involves stretching to hook onto the A and C strings to span under the strings below the bridge.  Some cellists place it on the winding of the string.   It is a little tricky to install as you will see after attaching one end to the A string, it doesn’t want to easily span the distance to the C string.  Looping dental floss through that second hook will give you something easier to pull on!   It has become less popular since there are so many options available now, and we have been special ordering as needed.