What length is this overflow pipe?

[deko]

Looking at getting a new waste for my bath, this one to be precise:

http://www.splashdirect.com/detail.asp/sku=SPL1812/c=407/d=31

But I can't make any sense of the technical drawing?

1) 380 + 450

2) 480 + 550

I can see 380 as the height, and I'm guessing the 450 is the total pipe length? If so, then how do I order the 480 + 550? There's an option for the extended waste (90cm)... but 480 + 500 doesn't equal 900??

 

[wms]

They come in two sizes to cover from 380mm to 450 mm and 480 to 550 mm measures as per line on drawing from centre of waste to overflow hope this clarifies.

if you look at the order numbers one is BT?????1 other BT??????2
which correspond with the lengths.

 

[deko]

380mm can stretch to 450mm? Impressive, could barely get 10mm extra stretching my existing overflow pipe.

Thanks wms

On a slightly different note, anyone know if these pop up designs (using rotating the wire) have trouble if the water level is anymore than ankle deep?