These organisms are free-living, typically very small and microscopic in size. Their bodies are cylindrical and covered with a hard coat, with both the anterior and posterior ends as narrow as a needle. This body coat is composed of thick elastin proteins. Beneath the body coat, there are four layers of glands. The mouth opening at the front of the body is surrounded and characterized by a lip. Additionally, two unicellular glands called phasmid glands may or may not be present at the periphery of the organism. The end of the animal is fatty.