Release of Security Interest

Recorded: 2011-05-24 Received: 2011-05-24 Pages: 6

Assignor

PNC BANK, NATIONAL ASSOCIATION

Executed: 2011-05-24

Assignee

420 THROCKMORTON, SUITE 1110, FORT WORTH, TX, 76102, UNITED STATES

Covered Properties (4)

Stepped Polycrystalline Diamond Compact Insert

Application: 10/600,662 →

Rock Bit with Channel Structure for Retaining Cutter Segments

Application: 10/419,589 →

Roller Cone Bi-Center Bit

Application: 10/210,806 →

Sharp Gage for Mill Tooth Rock Bits

Application: 09/773,884 →