The silica glass tubes are letter D. They are in a tiger top test tube. The clot activators like silica and celite are usually placed in this type of tube. This is usually inverted 5 times in order to gain the needed information. This type of tube is used is normally used to test serums and so much more.
Those that are in the red top tube do not contain any coagulants and additives. Like those that are in the tiger top test tube, this can be used for testing serums and also chemistry tests. Silica is known to be very helpful for bone growth. This can help the body develop well. Children usually have high levels of silica but this lessens when people get older.