I've actually found those Morrison's bulbs (the 20W and the 30W) kick out a crap load of heat compared to bulbs I've sourced from elsewhere. Actually it's just ridiculous the amount of heat their £4 30W 2700K bulbs kick out. It seems nearly twice as much as my £12 6400K bulbs which I got off teh intraweb.
Maybe you get what you pay for in terms of efficiency. I'd love to be able to accurately test it.
And asdfkry - those cases 'round the outside of the bulb are designed to "diffuse" the light, providing a more ambient light effect rather a spot light-like effect. Makes it easier on the eyes - probably less efficient for growing but who am I to say without the data to back it up eh
![Stick Out Tongue :P :P](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)