Bottle Trap Sizes

[Shutpa]

Am about to order this corner basin from B & Q:
http://www.diy.com/nav/rooms/bathro...68223&ef_id=UdHqlAAABDHtZ4Sx:20130820184733:s

and am wondering if this bottle trap would suit:
http://www.diy.com/nav/fix/plumbing...11598195?skuId=12108901#ancBVReviewsContainer

I note that the traps come in sizes of 25, 32 and 40mm. Does this refer to the diameter of the pipe and if so, how do I determine which to choose?

 

[Burnerman]

That basin will use a 32mm waste, and your bottle trap should fit perfectly.
40mm stuff is for baths, and I've only seen the smaller stuff on caravans / camper vans and the like.
John

 

[Shutpa]

Thanks for the rapid reply - wouldn't like to have the wrong thing when the plumber arrives.