The following is the Help! part# 42002 from Motormite. This will need to be modified by drilling a 1/2" hole through one so that the O2 sensor won't bottom out. With both pieces screwed together, the length is around 2". These are the 18mm tapered part, but there is also a 18mm flat mount style part# 42009. These can be purchased from any autoparts house, like Kragen, Pepboys, etc. Any place that carries the 'Help!' Motormite brand.