From RawlPlug this is the R-RLK-P Rawlok bolt projecting anchor plug with mechanical expansion. The Rawlok all-purpose expansion anchor plug is best for use with medium weight applications and the design ensures maximum performance in various materials. To ensure you are using the correct expansion anchor plug each plug has the bolt and drill size marked into the sleeve of the anchor plus it includes an integral collapse feature providing maximum clamping force to the anchor plug.

An expansion anchor is a fixing which is mainly used in a solid base material that when fixed in place gives you the fixing required through the expansion of the anchor. A pre-expanded anchor is simply inserted into a drilled hole and when tightened exerts pressure (expansion within the hole to provide a solid fixing).