CAMP Copper Head
Here's what other sites are saying:
Available in either single or double, the Cassin Copper Heads are a necessity for any serious aid climber's rack. Ranging in size from 4mm to 10mm, Copper Heads are designed to be pasted into vertical seams and cracks that are too thin for nuts or cams. When crack size permits the use of a double, you can stand on the confidence of having the greatest vertical crack-holding power of any mash-able protection.