You can also use Owen Mumford's Autopens (blue for 2u, green for 1u). They're rubbish but they do fit Lantus carts.
I think I used the green one for a while. Was the number of units in a little digital display window?
I absolutely hated it!
What's not to hate?
clunky...
plasticky...
no dose redial if you make a mistake...
aggressive spring-loaded delivery via a fiddly sliding button...
dose numbers thoughtfully printed in an ink that wears of in the second week of use...
They are an absolute horror.