Ceramic Aquarium Shrimp Shelter - Small House Part # 12121-01
 
Size Approx - 5cm L x 4cm W x 5cm H  /   2" L x 1.5" W x 2.25" H 
Provides refuge and protection from predators
Can provide substrate for fine algae and/or bio-film
Seclusion for molting / female with eggs