Yes, as Jocko says there are two different types, and they are also sided - so there are 4 different ones in all.
I fitted a Borg & Beck (Firstline) motor factor part to ours a few years ago, and it's been fine - cost was less than £10.
Avoid the no-name ebay ones, they are junk. If you want the best aftermarket, buy Delphi - but they are around £15-20 each.