Measure the diameter of one of the pins with a micrometer. If it's in the range of .152 - .156" (approximately) then you have small pins. If it's .168 - .174" then you have large pins. Large trigger pins are almost exclusively a Colt phenomenon. If you have a non-Colt lower they are likely small. If a Colt, then it gets muddy. Best to measure to know for sure.