Is this a 15w bulb

Hi all

I'm trying to source a replacement bulb for my garden lights but not
having 
much success.The local garden centres no longer stock them :(

The bulb needs to be a 12V 18W wedge type but the closest I've found is RS

Components code 106-486

Could someone confirm that this is a 15w bulb as it only gives a current 
rating (1A) in the spec  (Also what's the difference between T1, T3, T5 
bulbs ?)

Alternatively if anyone knows where I could get an 18w bulb (in the UK)
then 
please let me know

Cheers

Jim