this rear bicycle lamp arrived very quickly and once unpacked was contained in a small box the size of the size of a cigarette pack. This was the the thing that surprised me most really, the small size of the whole thing. It came with 2 AAA batteries and you have to use a 2P coin or similar to prise off the front red coloured lens to access the main unit and to load up the batteries. When fitted the lamp is switched on and off very easily by a red coloured microswitch on the bottom of the unit. One press for on constantly, second press for all three lamps flashing simultaneously, and final third press for each LED flashing on and off in sequence. The lights are very bright indeed and although I have not been able to test them properly yet as my bike is off the road at the moment I would have thought they were ideal for safety and visibility purposes riding at night. The package is the light on instructions but the light unit itself clips easily into a strong plastic clasp which I guess secures around the seat post - there is a smaller clasp which I suppose is to use on one of the seat stays as well if you prefer. Everything is quite easy to do and for the price including free postage and batteries I think this is a very good deal.