Can someone help a clueless idiot out? I don't know shit about electronics.
My car's speakers died due to water damage and I need to replace them. The new tweeters don't come with a built in high pass filter but two crossover boxes. I don't want to rewire everything and thus need to put the high pass filter into the A-pillar just in front of the tweeters. From what I can tell the provided crossovers pass the full range signal through to mid/subwoovers anyways, so leaving it out won't be a problem, but they're so absurdly big I can't fit them in there and need to rebuild them.
Pic related is the circuit diagram from what I can tell. I don't really need the ability to switch in the 3 Ω resistor (and I don't know what the fuck the inductor is supposed to do here). Apparently this is called a Butterworth filter or whatever, but all the diagrams I can find for those look different.
I don't know what the top component is. The two options I came up with are
1.) thermistor to switch in the 2 Ω resistor to stop the tweeters from getting fried in case the amp puts out more power than they can handle (seems reasonable). But this and the next option look the same, and the print on it (double squiggly line X50 OMOA) isn't helping
2.) ceramic capacitor in the pF range to do ???

From what I can tell that leaves me with three options
a.) Before I cracked this thing open I thought this was all I needed
b.) If the unknown component is a thermistor this seems like the prudent thing to do
c.) They probably had a reason to put the inductor on there?
The more I have to cram in there the less durable it's going to get, and I can't etch a new PCB, so I'll just have to solder components together in series with the wires, wrap it up in foam and tape and hope for the best, so ideally I'd want to go with a.) or b.). But I have no clue of c.) is necessary.

TL;DR: What's the round, brown thing? And do I need the inductor for a high pass audio filter?