Yes there are many manufacturers of these protector modules and they are all interchangable. The gas tube versions always have the screw cap painted white.
Aw, United is still around, it's just now Sprint, I mean Embarq, I mean.......
I am "barqing" as we speak. I kicked the Comcast cable modem to the curb. UTS actually ended up building a pretty good "data" department. I worked with them a lot in the 80s. UTS also held the price on a pay phone to a dime way up into the 80s. For a non-bell company they really did a very good job. Sprint did not carry on that tradition. They ended up uning contractors for most of their service and that was pretty spotty. Some guys were OK, others were slugs.
Here's an old G.P.O. document showing the protection which used to be employed on British telephone lines, both at the subs premises and at the exchange:
