I don't know whether tey're obtainable in you5r part of the world, but I have had good experience with Hecht/Assistent.

As for size, we put them into 24-well dishes, so max. 13mm diameter round coverslips work. At least disinfect in 70% ethanol and dry well before use; if cells do not want to attach properly, treat with HCl/Ethanol followed by extensive washes in 70% ethanol. See also this thread: https://www.researchgate.net/post/Why_do_hela_cells_only_die_in_imaging_dishes?cp=re65_x_p2&ch=reg&loginT=ZCGOnSG_6L78bGZ42vPw6DgGsiCpixORvRwNAZFGvfs%2C&pli=1#view=525511d9d11b8b4038e4b3d1; there is some more information on this theme.

The manufacturer really shouldn't matter all that much if you treat the slips properly. Coverslips can have variable indices of refraction, though, so they can affect things like TIRF microscopy depending on the manufacturer specs. Almost all of the glass in the world comes from a handful of companies, and other companies just mill the glass into cover slips, etc.

For imaging we normally use Mattek dishes, with glass bottom. As Daniel mentioned they have dishes with different index of refraction on the glass bottom and you should be careful on which one you pick according to the objectives of your microscope. In our case the #1.5 works great. Good luck!

Certain applications like SIM and TIRF require a specific thickness of glass due to the refractive index properties. #1 is thinner than #1.5. If you have thicker specimens i.e 3D cyst cultures, you can gain a little more depth into the sample with #1 glass.

Warner make good glass

https://www.warneronline.com/product_info.cfm?id=11&alpha=a&name=Coverslip%2FCoverglass

Thanks for all the information. I would also like to know if I can directly use 6-well or 24 well plate for neuronal cultures. Since these are also poly-l-lysine coated, it will be much easy for me to grow them on 6 well.

Are you thinking of using the same 6-24 well dishes for microscopy? They would need to be glass bottom- which is $$$.

http://ibidi.com/xtproducts/en/ibidi-Labware/Open-Slides-Dishes:-Removable-Chambers/12-well-Chamber-removable

(they offer coated options- but PLL is dead easy to coat onto dishes, I'd save your money!).

Ibidi also offer a optical plastic- which I personally wouldn't use- but I know of some labs doing simple fixed immunofluorescence with them. I prefer glass coverslips....

Multiwell chamber slides become problematic with live cell studies- it creates issues as the oil becomes quite sparse if you use more than 4 wells at a time (the immersion oil needs to be replaced in between samples). I prefer to use the 4 well glass bottom dishes for multi well applications: http://www.invitrosci.com/products_by_category.php?cat_id=301

I am referring to these type of plates which we use for seeding:

http://www.sigmaaldrich.com/catalog/product/sigma/cls3516?lang=en®ion=PK

I want to grow my cells in these well plates and continue microscopy with these by fixing them. It wil be time consuming for me to order poly-l-lysine coverslips. I wish to continue using these well plates. Is it ok? will my neuronal cultures be fine with such plates?

You can't use plastic bottom dishes for ANY oil immersion objectives.

Most 40x, and all 60x and 100x use oil.

It has to be glass due to the refractive index properties of oil and the mounting media your specimens are in. You want to bend the light as little as possible- such that you get little aberration in your imaging. This is achieved by matching the refractive index of everything in your light path- oil, glass and mounting media. Microscope objectives are designed with this in mind.

I.e you use plastic- the images will look fuzzy.

see figure 2 on this page

http://www.microscopyu.com/articles/optics/waterimmersionobjectives.html

I went through that. Thanks a lot. But atleast I'll be able to get something, some pattern of cell boundaries on DIC at 20X magnification?

Yes- on 20x you'll see green cells but not much detail. Remember to take the dish lid off for DIC, or use a glass plate.