This genuine Atlas RL41 UV lamp is the standard lamp replacement for the Atlas L41 UV unit.
The 39W UV lamp gives a 30mJ/cm² dose at the end of UV lamp life at 1 year. This means that you will get slightly more when you turn the UV lamp on for the first time, and from there it will reduce downwards. After the year, it is not seen as being effective as a disinfectant.
The Atlas RL41 UV lamps are fragile and the glass should not be touched, this is for the same reason as car headlights. The UV lamps run hot and the oil on your hands will mark the glass and create a weak point. If you have to touch the glass part of the UV lamp, you should wear gloves.