Geissele makes models with large and small pins. Try their website for more info http://www.geissele.com/
. Below is a some info from their site. I hope this helps.
*NOTE: Colt receivers with large pins (.169" dia) require our Large Pin Trigger. Our Large Pin Trigger will not work in a lower that has a Sear Block. Some early Colt receivers and all other branded receivers (Bushmaster, Armalite, Rock River, Olympic Arms, Eagle Arms, PWS, Stag, CLE, etc) use the small pin (.154" dia) that our Small Pin Trigger is designed for.