Replaceable tip probes are used with aqueous samples. Replaceable tip probes have threaded ends and when the tip is worn out it can be unscrewed and replaced.
If you sonicate a solution that contains organic solvents, alcohols or any low surface tension liquid, the liquid will seep inside this threaded tip (regardless of how tight the connection is attached). Once liquid gets inside the tip, it will loosen and cause the Sonicator to overload. If you are processing a sample containing solvents or low surface tension liquids you must use a solid tip probe. Solid tip probes can be used for any type of sample.