Ceramic Aquarium Pleco Cave Breeding Shelter - Triangle Part # 11991-01
 
Size Approx  11.5cm L x  5.5 cm W x 4 cm H   |   4.25" L x  2.25" W x  1.25" H 
1 - Top Entrance Holes @ 5 cm x 3.5 cm   |   2" x  1.25"   
Provides refuge and protection from predators
Can provide substrate for fine algae or bio-film