SEEKUPThick Silicone Breast Gel Pads Bra, Transparent Large

Q: Can you place these inside a bra like a normal bra pad

Yes you can. This is how I wear them. Get yourself a good sturdy bra with cup room and these fit perfectly. However if you choose a tiny bra or one without enough room in the cup area, these will slide right out. So bra choice is important. But, I love these things. Try them!

Q: What size should I order if I’m 36b?

I believe there one size fits all. There meant to give you extra lift, adds more cleavage.

Q: What size insert for 36C?

It depends what you are starting with. These add to what nature gave, the small will add about 1/2 cup size, medium adds about 1, and I haven't tried the large.