I'm still waiting on mine to arrive from RCI, but just based on the pictures I would argue they don't protect too well. You can clearly see the cat in the pictures with the trans skid installed.

RCI did come out with a cat skid addition that bolts onto the trans skid. You can drill mounting holes in the trans skid to accept the cat skids. They wouldn't have done this if the trans skid alone did an adequate job of protection.

Got mine and installed it yesterday... pretty happy with it.

That looks great! I just got the email today that mine are ready, and I just gotta find the time to go pick them up and install them. Not enough hours in the day!

The Cat seems pretty well protected from off-road damage before adding the special cat skid. If your getting this to deter theft, I’d rather just use my $100 comprehensive coverage deductible in the off chance someone steals mine. Whose to say the theif still wouldn’t just sawzall the skid and still take the cat anyways.

These cost $150. I'd pay that to insure I don't have to spend hours dealing with police, insurance and repair shops, assuming they even have a new Cat for me to purchase...
Not to mention using your comprehensive generally makes your rates go up. Especially for people who are getting hit multiple times.

Catalytic converter thefts lead to part shortage, higher costs

Ok sure if they were after MY cat in particular that could happen but it would take many many minutes. No sawzall is going through this easily... that's the point.
Also the point is to make your vehicle a hard target so they just move on to another one that would take 1/25th the time.

But whatever... It's easier for me (and to most who are asking in a thread entitled - "best skid for cats") to spend $150 and be done with it.

I found these CAT shields from CaliRaised where they state they work with 99% of aftermarket skids. I have a full set of C4 skids, so I’m waiting for a reply from them on Monday. Less than $200.
Catalytic Converter Shield Fits 2014-2023 4Runner
– Cali Raised LED

I too was worried about someone crawling underneath my 4R and attempting to steals the cats. I purchased the Talon's Garage skid plate that blocks access to both cats from underneath and from the sides. Fitment was not an issue and after one year of use, it still looks new. I also like the the air venting holes directly below the cats which alleviated my concerns for heat.