I think you are talking about cleats. If that is the case then yes, they are safer than metal but wear out sooner. Also the shoe must be the interchangeable kind.
If they appear to be in good condition, then NO, do not replace them.
The density of rubbers stoppers can be very different from one to the next. This is because there are different stoppers at different densities.
NO!
Normally cork or rubber is used as a stopper in a flask.
There are many formulations of rubber, so it depends on which formulation of rubber you use. Pharmaceutical rubber stoppers are made of Butyl rubber which is unaffected by alcohol.
Heating at high temperature can be dangerous.
use to cover the test tube, basically like a cork.
Commonly, rubber stoppers are used in scientific experiments to plug and test tubes. Their purpose is to prevent liquids, and sometimes gases, from escaping their containers.
Rubber stoppers are widely used for the commercial, industrial and scientific markets. They are made from different types of rubber and available in various sizes and styles depending on applications.What are Rubber Stoppers used for?Possible uses of rubber stoppers are wide and varied such as :Mechanical StopBumpersVibration MountGrippersClampsSticky feet for platformFits into Test Tubes, Boiling FlaskPipe stoppersPaint masksTube plugsDoor stopperThe kind of rubber stopper used in chemical laboratories is a plug which fits into the top of a test tube or flask, often with a hole or holes bored in it for the insertion of a piece of glass tubing. They used to be made of cork but rubber is less likely to disintegrate and get into the contents of the flask or tube.
Rubbers stoppers are used in laboratory for: - to close bottles - to close tubes - to make a link between tubes or other laboratory objects - to make link with perforated stopper
Replace rubber washers and possibly metal seats in the faucet
to bore holes in rubber stoppers or to cut out pieces of agar in Petri dishes