There are many different types of test tube clamps. Some varieties of test tube clamps include Stoddard test tube clamps (five-inch length and made out of brass or nickel), Semi micro test tube clamps (rounded jaws and nickel-plated steel wire), wooden test tube clamps (inexpensive and terrific for educational demonstration) and several others.
Test tube clamps are advantageous because they are safe to use, especially during the heating process as well as for dealing with harsh and potentially dangerous chemicals inside of test tubes. Test tube clamps also have very firm holds of test tubes and can be easily moved around.
Test tube clamps are not only used to secure test tubes in place, but they are also often used to hold up burettes and distillation condensers. A lot of efficient test tube clamps come with finger gripping, which is a rubber coating on the jaws of the clamp that can improve your grip so you don't drop the clamp.
Purchasing test tube clamps is generally an inexpensive endeavor. If you are looking to purchase a single test tube clamp, you can expect to pay around $2 for one. If you want to buy many test tube clamps in bulk, expect to pay around $20 or less.
Many online vendors have diverse selections of test tube clamps for educational and scientific purposes. Some good places to check include Nova-Tech International, BLD Science, Cole-Parmer, Microscopes.com, SK Science Kit and Boreal Laboratories, Academic Superstore and many others.