I've got the Campfire Audio Vega, which I find notorious for creating a hard vacuum seal for pretty much any tips I try that aren't foam. Since the foam tips cause some pretty severe irritation in my ear canals, and every silicone tip I try loses audio due to negative pressure in my ear canal, I've been restricted to the stock black silicone tips. Something about those tips doesn't feel fully silicone to me, as they tend cause irritation if I don't swap them out every other day and wash them regularly. I tried the Symbios, but had the same problem with the vacuum seal. After getting frustrated and being stuck with just one tip option, someone reminded me about venting the bore. It seems that everyone uses some piece of paper or foam, that's hard to cut and place. One of my hobbies is knitting professionally, so I thought... "why can't I vent the tube with a fiber?" I grabbed a piece of cotton yarn and it does a great job at balancing the pressure w/o sacrificing sound quality. Ultimately, I found the Symbios a bit bright (W-bore), and too firm for my ears. So, I've gone to the RHA stock silicone tip (med). It's a perfect fit, does not irritate my ears, and no longer cuts off all the sound due to negative pressure issues. I was asked to take photos, so figured I'd share them here. Using a cotton type thread/yarn is great, because it's much easier to place when using a length of yarn vs. trying to place a tiny piece of foam or what not and getting annoyed at it not landing correctly. It also seems like the air is venting through the fiber rather than through any open gaps created by other mediums.