For sale is the actual piece in the picture with a ruler for size comparison.
 
General:
Cork bark is a popular material for use in terrariums, as it is a natural, durable, and attractive element that provides a variety of benefits to plants and animals kept in enclosed habitats. Cork bark is the outermost layer of bark from the Cork Oak tree (Quercus suber) and is widely available in various sizes and shapes.
When used in a terrarium, cork bark provides a natural-looking background that can help create a more realistic and aesthetically pleasing environment. The bark is also a great way to add texture and dimension to the terrarium's landscape, allowing for various climbing and hiding spots for the animals.
One of the unique features of cork bark is its ability to retain moisture without becoming waterlogged. This makes it an excellent material for creating a humid microclimate within the terrarium, which is essential for many species of reptiles, amphibians, and invertebrates that require high humidity levels to thrive.
Cork bark can also be used as a substrate for growing plants, as it provides an excellent growing medium that retains moisture and allows for good drainage. The bark's natural texture and porous nature also make it a great place for beneficial bacteria to colonize, helping to maintain a healthy ecosystem within the terrarium.
Overall, cork bark is a versatile and practical material for use in terrariums, providing many benefits to the plants and animals that inhabit them.

Cork Bark & moss:
Cork bark can provide an excellent substrate for moss growth in a terrarium, as it is a natural and porous material that can retain moisture without becoming waterlogged. Mosses are small, non-vascular plants that thrive in humid environments, making them an ideal addition to a terrarium's ecosystem.
To grow moss on cork bark, you can either attach it directly to the bark or place it in a layer of substrate that includes moss-friendly materials such as sphagnum moss, coconut coir, or peat moss. To attach the moss to the cork bark, you can use a thin layer of adhesive such as silicone or hot glue, or simply press it onto the bark's surface.
It's important to keep the cork bark moist to promote moss growth, as mosses require consistent moisture to thrive. You can mist the cork bark and moss regularly with water, or create a humid microclimate in the terrarium by covering the cork bark with a layer of plastic or glass to help trap in moisture.