This is a double cardan, (not cardigan—that’s a sweater) or CV. This type of joint houses two identical U-joints within a coupling that operates the U-joints in equal, but opposite angles. These opposite angles cancel out opposing vibrations for smoother operation. Somewhere along the line “the man” stopped making these things greaseable. We’d like to “grease” the penny pincher responsible (not literally, we are lovers not fighters) because they last much longer when they are greased regularly. Most typically max out at about 30 degrees of angularity. The longer a shaft is the more wheel travel you will have without a CV or U-joint binding.