In the provided image from Stadium-arcadium, Flea is seen using a Specter NS-2 Bass while recording the "Mother's Milk" album at Ocean Way Recording Studio in Hollywood between 1988 and 1989.

In this picture you can see Eddie playing a white ns-2

at 1:36 Used during Black Album recordings

Geezer Butler, acclaimed bassist, is confirmed to have utilized the Spector NS-2 bass guitar during his performance with Ozzy Osbourne at the Moscow Music Peace Festival on August 13, 1989. This is evidenced by footage provided by ThatRemasterGuy on YouTube, showcasing Butler playing a white Spector NS-2 throughout the event.

Sting played this bass throughout the 1983/84 Synchronicity Tour and was his main bass that he used.

Duff is seeing playing this bass on thr Live Ritz '88 show, as he said post on an interview for Total Guitar Bass Special Issue 2, April 2004:

"I had a real bad experience with an active pickup. When we filmed live for MTV at the Ritz, the first song was It's So Easy. Kramer gave me this bass they wanted me to play and it was active. It's So Easy starts off with dnnna dnnna dn dnnna dnnna dn (sings opening bass figure and air fingers the bass)… The bass stopped working so I threw it and got my Fender back. So from then on I want my bass with a cord going into an amp; if it's two amps that's fine. And I'll probably play live that way."

About the Spector Guitar in case the name kramer make some confusion:

Spector Guitars

In 1985, Kramer purchased the Spector guitar and bass company. It should be noted that during this time, Kramer was doing extremely well and was well on the way to becoming the biggest domestic manufacturer of electric guitars thereby, putting them in a position to buy out smaller companies in an effort to expand the size of it's base.

http://www.vintagekramer.com/spector.htm

Here is a pic of the bass http://i1163.photobucket.com/albums/q551/guitarhousenet/NS2%20Black%20Kramer%20Era/BlackNS2FullFrontw.jpg

Here's another pic of Duff at the Live Ritz: http://image.noelshack.com/fichiers/2011/32/1313325702-kramer.jpg

And here is the live video: https://www.youtube.com/watch?v=qix7JNA_Y70

In this video you can see the NS-2 bass he used. Definitely sounds like he favoured the bridge pickup sound over a fuller rounder sound, that's why for most of images and words his tone cuts.

This video from SkullsNBones.com shows bassist for Pantera, Kill Devil Hill, and Down, Rex Brown at a bass clinic with his new rig, one item of which is the Spector NS-2™ Bass in white. The majority of his newer appearances show him with this white Spector. He in fact actually plays this bass more than his Signature Spector Rex Brown Bass.

David is seen playing a pre Kramer, Spector NS-2 in black with golden hardware. This bass was used to record the 4 string parts on the album Cryptic Writings.

While there seem to not be any live photos of Gene with the Spector NS-2, there are these from Asylum tour book and a video or two.

The official Spector website states that Inez uses a Spector NS-2.

Throughout the video we can see Mike playing his sunburst Spector NS-2. He also owned a white and a black one.