Trulock Tru-Choke SD Pattern Plus 12 Ga Improved Cylinder. This choke tube by Trulock is essential when you want to etch a design in your muzzle. The True Lock Tru-Choke Pattern Plus Choke Tube was specifically designed and crafted by professionals who know exactly what you need and want out of your tools. When you're doing changes on your piece you want to make sure you have something reliable; you want to make sure you have Tru Lock Tru Choke S.D. Pattern + SD Choke. Specifications for Trulock Tru-Choke SD Pattern Plus Choke Tube: Manufacturer: Trulock Gauge: 12 Choke Tube System: Tru-Choke Package Contents: Trulock Tru-Choke SD Pattern Plus Choke Tube Trulock SD12720: Tru-Choke SD Pattern Plus 12 Ga Improved Cylinder