UVB bulbs can be dangerous to you if your under it for more then 10mins, as they are essentially the same as the tanning bed lights, now they will deff give you a fair good amount more crystal formation on your buds and I'd say is even liked/loved by your ladies as the sun puts out UV rays (sunburn anyone?) so they obviously have evolved and adapted to this, for amount I could say as I havn't had a chance to use em yet (will soon though) but it would be interesting to see if different strengths of UVB bulbs help (IE.. both 25 and 50watt) as the sun also changes in strength depending on which side of the earth it is facing.