The lockblocks let you attach a tubular object (eg a torch or bike pump) to another tubular object (eg handlebars or frame of a bike). Different models are good for attaching at right angles or in parallel. You can get them from the www.fenix-store.com site.

I also have the L2D CE (AA version), the 135 lumen one rather than the brighter one they are advertising now. It is brighter than a Cateye 530, looks slightly dimmer than 10W halogen but not by much. Very much more convenient than either of the others, except that battery life is about 2.5hrs with 2500NiMH (compared to maybe 10 hours for the 530). Works reasonably well taped to my helmet as a headlight; the weight is manageable, I currently leave it on for all my riding though I'd take it off for a really long on-road ride.