Ok London, if you are (finally you've said its for a Tenere) referring to the Tenere, there are 3 stages which require 4 bits to achieve the max performance these are as follows in order of stage:

Main Filter High Flow replacement (Stage 1)

http://www.e-dnafilters.com/Product.asp?ID=810

Stage 2 (a) - Snorkle replacement and airbox intake module:

http://www.e-dnafilters.com/Product.asp?ID=824

Stage 2 (b) - Side Cover - High Performace filter:

http://www.e-dnafilters.com/Product.asp?ID=1211

Intake insert - which combined with Stage 2(a) and Stage 2(b) will equal Stage 3

http://www.e-dnafilters.com/Product.asp?ID=1243