How many sensors are needed for 2015 chevy impala 3.6 v6 flex fuel lfx engine?

They are 4 sensor in total. Two for each catalyst converter.

What size socket do these require?

You will need 7/8-inch (22mm) Offset Oxygen Sensor Socket. Thank you for contacting us

Does this 02 sensor come with the removable tool ?

this will not come with it, you have to buy it eleswhere

How do I specify that I need them for downstream ?

Your downstream O2 sensor looks different from your upstream. So you need to look at the ones you have on there now. But,from my experience it is best to buy a set of the same brand than to mix name brand sensors. UsE all 4 of th e we m rename the brand sensor on my your vehicle. Hope this helps you. Very Respectful, Customer

Manufacturer	Vinrold
Part number	24773 - 250V
Item Weight	150 g
Package Dimensions	15.09 x 6.2 x 6.2 cm; 150 g
Item model number	250-24773
Style	Modern
Plug profile	Flange Mount
Specific uses	Oxygen O2 Sensor
Included components	1 Piece Oxygen Sensor
Batteries included?	No
Batteries Required?	No

Vinrold Oxygen O2 Sensor Downstream or Upstream for 3.6L GMC Acadia Chevy Camaro Colorado Equinox Impala Cadillac CTS SRX STS Buick Enclave Suzuki XL-7| 250-24773

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