help choosing the right equipment for a second hand 5 gal carboy

So I recently told a friend of mine that I brewed a not crappy batch of beer. He informed me that he had one glass carboy (containing exactly 1 dead mummified mouse) and one what looks like plastic bottling bucket, but one that comes with a airtight seal (minus 1 o-ring), that I don't recognize, so I don't know exactly what to make of the latter.

Anyways he traded me the equipment for a 12er of my not so terrible first batch and promise of another 12er of my second batch. I thought it was a fair trade.

I have run into a problem however, I can't figure out what stopper to buy for my carboy.

I was sold on this one,

http://www.northernbrewer.com/brewing/universal-carboy-bung-drilled.html

but then I thought 'Well lets see what my new friends at HBT have to say'

so I searched per the advice to newbies, and I found this:

https://www.homebrewtalk.com/f137/unknown-carboy-caps-119285/

1) I don't know what the second is talking about, maybe I'm missing something fundamental but I searched unknown carboy cap and got this guy:

http://cgi.ebay.com/Universal-Carbo...emQQptZLH_DefaultDomain_0?hash=item2302784c33

Which I think is what I should be looking for...

2) In either case, if I want to make a blowoff tube, which size tubing do I buy? Does it matter?

So which one should I purchase? The northernbrewer one is attractive to me because it's sold from northernbrewer so I can lump the shipping together with my next ingredient kit (three hearted ale), and I also plan on buying a bigger spoon (we're gonna need a bigger spoon.)

The second one though if the product reviews hold, is the far better option, despite it being 4x the cost plus additional shipping which is the cost of the item itself.

So where do I go good HBT peoples? Thanks in advance.

I don't think the second guy knows what he's talking about either.

That carboy cap from ebay does a good job with Better Bottles. Most glass carboys have a smaller bung though, so I doubt it would fit. The one from Northern Brewer claims to work though. The stoppers that I have for my glass carboy are 6.5 drilled rubber stoppers.

for a blow off, I like to use 1/2 ID tubing. It fits nicely over the center portion of a three piece airlock with no straining. I've seen where other people use 3/8 inch tubing and heat and stretch it over the center post in the three piece, but that just seems like extra work to me.

So really I don't need to buy anything as long as my tubing that I own fits over the center piece of my airlock? Well thank you sir for saving me 4 bucks! Northern Brewers it is!

Yep, the only requirement for a blow off tube is that you can connect it securely to your three piece (or if you're using the tube straight into the neck of the carboy method, fit securely into the neck of the carboy). Anything beyond that is preference.