The Geissele Super Dynamic-Enhanced (SD-E) Trigger featuring an exclusive flat trigger bow, is a finely-tuned two stage trigger providing enhanced trigger control and weapon accuracy while maintaining the robustness and reliability of our combat-proven two-stage trigger. Note: *COLT 901 RIFLE USERS PLEASE SEE ARMORS TOOLS FOR PINS (PART# 02-269) THAT WORK WITH THE WIDER RECEIVER.