Stock 2009-2011 GTR turbo inlets measure 1.75" ID and have proven to be a restriction even in stock GTR's. The stock 2012+ turbo inlets measure 1.95" - 2.0" ID, which is an improvement but still doesn't match the size of the compressor housing inlets properly. These BP Ported inlets are 2.1" all the way through, are polished to a super smooth finish to promote flow, and match the compressor housing inlets perfectly.