This has got to be junk, right?

Firefield T180



T180 Tactical Mini Flashlight Kit // FF73011K

These are all over the place at about $30.

In the quest for lighter and lighter components, what is your suggestion for a lightweight carbine light that is durable?

Yeah, cheap lights are usually junk.

The best lights I've seen are Elzetta. They have a solid acrylic lens/reflector and fully potted electronics. You can literally disassemble them then reassemble them under water and it will work just fine. Needless to say they are also waterproof. I've seen videos of them being abused beyond any natural abuse and they still function. I've owned Olight Warrior lights and while they did work, they have quirks. Didn't work well with rechargeable batteries. My next light will be an Elzetta for sure. I'd take Elzetta over SureFire.

I believe Olight Warrior has worked out most all of their quirks with their newer models though. They also added some new quirks like their glow in the dark reflector (silly), their cheesy blue bezel and stuff like that. After having gone through a couple of 'ok' lights ... I learned that you do get what you pay for. I've had them crap out on me in the middle of the night, under stress, when I needed them to work so next time I'm getting Elzetta.

I've heard good things about StreamLight lights from Primary Arms. I considered getting one of them due to their affordable price, but still leaning toward Elzetta for ultimate quality & reliability.

Modlight

china is asshole

that being said, i'd go with an arisaka 300 series light and arisaka mount. whole thing should be ~3.5oz, and will be basically bomb proof

Arisaka 300 e1ht series.
Modlight plhv2 (general purpose) or okw (lightsaber) 18350 series.

Inforce are pretty light. Built in pic clamp. 4 oz.

My favorite lightweight carbine light is the Arisaka 300 series.  I have an Inforce WMLx Haley strategic that I was given.  It is fine but I like the Arisaka way better.   Either would be ok for inside a home, but the Arisaka has way better throw if you end up dealing with a problem outside.

I know a lot of guys like the streamlight lights but I'm not sure what model.

If you can justify and stomach the cost, I say a Modlite PLHv2 18350. I've gone through a lot of lights and honestly Modlite has been coming out on top in performance and product.

True story

To expand on my earlier post:

If I were getting completely ridiculous, I would say Modlite OKW or PLHv2 head if you prefer that (I'm partial to the OKW since it works fine for indoors and the throw is amazing), reptilia torch 18350 body, and arisaka momentary only tailcap.  Since that ends up being a pretty expensive light, I am fine with arisaka 300 + an arisaka scout light mount for a basic carbine.  

FWIW I have Modlite OKW, Cloud OWL, Arisaka 300, Arisaka 600, surefire 300 (old one), surefire x300u, and Inforce WMLx mounted on various firearms.  They all function absolutely fine for moving in and around buildings, but the modlite, cloud, and arisakas are much better choices if you need to use them outside at just about any distance.  The modlite wins for being able to see stuff at long distances.  The Cloud OWL does a good job of that and also wins at being physically upsetting to be spotlighted with out past 100 yards.  

That said I don't blame anyone for not wanting to spend hundreds of dollars on lights.  For a much more budget friendly option I think the Inforce 800lumen WMLx is very nice (just don't expect to be able to see much past 50 yards with it), and supposedly there are good streamlights out there as long as you don't use the pressure pads and stick to tailcap activation.  Cheaper than that, I would look for a ring mount + a Klarus or something.