Why is BC=8.4 so rare?

Every contact lens I'm looking at is BC=8.6 or more.

8.6 doesn't fit me. I have tried so many brands of 8.6, they work fine on my left eye, but are way too loose on the right. They move a lot with every blink, and my eye begins to hurt.

8.4 fits me fine, but I'm having a very hard time finding an 8.4 BC lens in the silicone hydrogel category.

I can assure you, 8.6 won't fit in my right eye, i have tried so many 8.6 lenses, they invariably fail, and All 8.4's have worked so far.

Could you please name some silicone hydrogel lenses (monthlies) that are available in BC=8.4?

I'm in India, and doctors here are absolute MORONS. They don't even measure the BC, and don't do trial lens fittings. If you ask for a contact lens, they simply write the power, no BC, no DIA, nothing. The patient is free to purchase whatever lens he wants. And retailers here don't require a CL prescription as well, you can randomly pick a CL from an online store or any eyewear shop.

I figured this "8.4 works" by trial and error, no trial lenses, i just kept purchasing boxes and throwing them away, until i found one box that doesn't hurt my right eye, and that's 8.4.

Since then I've tried a couple more brands with 8.4, they all have worked, but none are silicone hydrogel.
Please give me names of some 8.4 BC silicone hydrogel lenses I can try out and check if they feel comfortable.

thank you.

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