We have combined our electro-polished 3.5 LB. Drop-in Connector Trigger with a Wolff 4.0 LB. firing pin spring, a Wolff 6.0 LB. trigger spring. These combinations will give you the lightest smoothest drop-in trigger assembly you can buy! And you save some money! Not for self defense if you use the Wolff 4.0 lb Firing Pin Spring. If you want to use for self Defense or in a 10mm/45 caliber Glock use the Wolff 6.0 lb firing pin spring.