Two thoughts:

- Modern glass knobs aren't always well-made. Since these are glass, it'd be smart to pick up a couple extras to tuck away in case of breakage.

- You say knobs, so I'm thinking little balls. I have no idea how old you are, but IF aging in place is an issue, consider that those are more difficult for elderly hands to open.

What ever you decide, consider adding backplates to save your cabinets from gouges made by fingernails, dirt from hands, etc. Backplates are an awesome way to save your cabinets from wear and tear. I love mine.

I don't think glass knobs are very good in a kitchen, for many reasons.

Whatever you use, use the same on all your cabinets and drawers - same size, too.

Why have the holes been drilled before you have even selected your pulls/knobs?

Watch the spacing between the back of the knob and the cabinet. I had a rental once that had knobs shaped like discs, they were flat on the back and there was enough room to slide your finger in behind the knob but not enough room for your finger to roll over in that gap as you moved the door.

Lemme explain in a gruesome way ... if you took a cross section of your finger you would see it is oval shaped. If the knob is so close to the cabinet that you can't fit the finger behind it from any direction/angle/approach ... you will hurt your finger when you are moving too quickly and try to twist your hand before completely removing your finger. So jam your finger in behind the knob & try to roll your finger, see if the knob bites you.

I hated those knobs.

Make sure the knobs project far enough out so that your fingers don't touch the wood doors/drawers when opening. Grease/dirt/oils, etc. from hands can stain your cabinets where the knobs are attached.

I honestly do not like knobs. I dislike the fact that eventually they start to just slip in place. I prefer pulls in my opinion. Look at Restoration hardware. They have beautiful lines of glass knobs and pulls. Share pictures of what you have and your ideas.