PRO-4 Square End - Series 190 Series 190 Square End Vibration Reducing End Mill. The patented PRO-4 by PROMAX. View Speeds and Feeds page. Features: Eliminates Chatter & Vibration Delivers and Excellent Finish Relieves cutting pressure against the tools with OD Chip Breakers Easy & Inexpensive to Regrind Standard with Advanced AlTiN Coating (Part Number ends in 4) Standard with Advanced nACRo® Coating (Part Number ends in 5)