This is the Canon MP-E 65 f2.8 1-5x Macro, unusual in that it *only* allows macro and is manual focus only.
Magnification is from 1:1 (shown here) to 5:1. Working distance varies from just under 10cm at 1:1 magnification to around 4cm at 5:1.
In addition the lens extends a *long* way when operating at 5:1 magnification.