The gas spring struts that hold the lid open on my stainless steel Hammerhead 42" Toolbox (model 2002-1800) from Costco just failed.
Sadly, they leaked oil in the top compartment of the box, making a mess and melting the drawer liner. A big mess.
Amazingly I have the old toolbox manual and it lists the replacement as part number TB12U06. But I suspect I'm out of the warranty period.
The original struts measured:
eye to eye: extended: 350mm (13.8"), compressed 220mm (8.7")
stroke: 130mm (5.1")
10mm ball receptacle
I measured the force it took to compress one of the old ones on a bathroom scale. Of course it had been leaking so maybe it was a bit low. It seemed to take 15-20 lbs to compress it.
Removing the old struts just require lifting the metal band up a bit with a screwdriver and then the head pops off the ball.
I scoured the Internet and it seems gas spring struts like these are available, but the lowest force ones I found were 24 pounds each! The lid on my toolbox isn't that heavy, but I decided to try them:
Suspa 24 LB Gas Spring C16-06389. About $30 for a pair on Amazon. (See addendum at the bottom for a better strut option!)
Here is a pic of the old and new strut. The new one is on the bottom and you can see it is just a bit longer.
Installing the new strut requires you lift the band on the head just a bit with a screwdriver so the head can pop on the ball.
Here is a shot of the new strut installed:
And here is the strut in action. You can see it is a bit too strong, the lid really flies open!
If you can find them, I instead recommend struts rated for around 15 pounds each.
Addendum: As recommended in the comments, I tried some different 10 pound struts from liftsupportsdepot.com. The struts I bought were part number
SX140P10. These are also available through Amazon
here. I have installed these, and I much prefer how the lid now opens in a much more controlled manner. I suspect a 15 pound struts would be perfect, but these 10 pound ones are much better than the 24 pound ones I started with. Get the 10 pound struts if you can't find 15 pound ones.