Dremel 4000/6-50 6 Attachments, 50 Accessories High Performance Rotary Tool Kit with Flex Shaft features a high performance motor providing maximum power and performance at all speeds with the variable speed ranging from 5,000RPM to 35,000RPM and electronic feedback that auto adjusts power and speed for the most consistent performance and can be used with any Dremel accessory. Dremel 4000/6-50 6 Attachments, 50 Accessories High Performance Rotary Tool Kit with Flex Shaft features an innovated airflow system with ventilation mechanism that helps prevention of heat build- up for smoother, cooler, and quieter operation. Dremel 4000/6-50 6 Attachments, 50 Accessories High Performance Rotary Tool Kit with Flex Shaft features replaceable brushes to extend tool life and the slim/ergonomic body has a 306° grip zone for extra comfort.