Pretty much spec. to the pickup design-i try and get one that fits the tightest

 

Color. Blue is thin and Red is thick. Theres some others as well I havent used but have seen pics of green and white ( aftermarket Im guessing? ) Regardless I aim to use the red as default but sometimes it just wont fit without binding, in those instances I use the blue. In car swaps are a pita to up size and its easy to pinch/fold the o ring over. Speaking of which its common to mess these up so be cautious and careful that it goes in straight and true. Lots of oil for ease of install

 

it has to do with the pickup tube design... Indentation or flat
....

Indentation version gets Red, Flat style gets Blue

same kind of deal with Green and Black o-rings

 

Interesting. I never really looked to compare when i went from the truck pickup to the Camaro pickup. I used the red on the Camaro pickup though. I bought three seals just in case i rolled one. I have 2 left
Tommorow im gonna have a look at my truck pickup. I am pretty positive it has the blue seal.

 

S2H IS ON THE BALL!! Great info!!

 

Plenty of o ring leaking issues with LS1's and it's a common upgrade to step up to the red even with an f body pick up tube.

 

The correct o-ring I have found to be a very tight and snug fit. To go with the thicker o-ring it could be relatively easy to damage if forced to fit, and that could possibly lead to it failing down the track.

 

Thanks for the info.

 

^ Exactly. See my first reply