The Round version is a little bigger than the square, and comes with a butterfly clasp (I will include a rubber bung as well).
They do appear to be very hard wearing, tested with Isopropanol Alcohol and 100% Pure Acetone will no visable fading or marks.
Please note the dots you see in the photo are not visable on the actual image you will get.
If your worried about the cost of postage I have worked out that if you order up to 18 per order it should not cost any extra