Coop's Bowsmith Spine Tester Silver. The tester uses spring tension over dead weight for a more consistent and accurate reading. Also incorporates a built in arrow spinner so an archer can tune their broadheads. Specifications for Coop's Bowsmith Spine Tester: Manufacturer: Coop's Bowsmith Color: Silver Size: One Size Features of Coop's Bowsmith Coop's Spine Tester: Spine tester to optimize arrow flight by locating spine of arrow Uses spring tension over dead weight for more consistent and accurate readings Package Contents: Coop's Bowsmith Coop's Spine Tester Coop's Bowsmith Coop's Spine Tester