Hmmm.  I originally thought Systainers were a Festool thing.  But lately, I've seen it offered by other companies, so I was confused.  Now, I find out it's an independent company that partners/licenses to others, including Festool, Fein, Makita, Lamello, Haefle, Senco, Metabo, Wagner, Graco, Bessey, Panasonic, Husqvarna, Gorilla (Glue), and a bunch of others that I've never heard of.

 

https://www.tanosus.com/100/En/HOME/Products.html?utm_source=newsletter&utm_medium=banner&utm_campaign=protools&utm_term=2021-08-11

 

I have one.  Yes, one, that sits empty on the top of a shop cabinet.

 

 

I have a $5.00 generic one from Lowe's 

 I have one Festool product that I bought new. I bought it with a 25% Bing discount (if anyone remembers those) and then further reduced my investment by selling the systainer. As I recall I got $50 for it (!) which was a little more than 1/2 the cost of one from Festool. A lot of folks swear they are the greatest thing since sliced bread....to me it was just another plastic tool case. But like you, I though they were a Festool thing. Interesting.

I got a 150 sander on a promo for about $59.  It came with a Systainer.  I like the sander, but not sure I'd buy one at list price since I'm not doing refinishing jobs any more and it's twice as much as the Bosch that I've had for years.  The one thing I like about it is that the RPM don't rev up when you take it off to move from one part to the other (and the speed control is the trigger, not a dial, same as on my old Bosch)