Automatic Locking push button spindle, which was researched and developed by us, with built-in Precision Miniature Spring. The micro-spring exerts a pretension force on the Chuck that the bur would be more and more tightly held when the hand piece rotates at high speed, making sure no bur flies out in the process of Grinding. Specifications: - 8 holes (4 Holes air +4 Holes water ) - High torque - With LED. - Made in China.