These 15973 Studs are used to hold the 15889 Gear Pump to the Sump Base. The original design used Allen Head Bolts (M22339), then they went to these 15973 Studs. There was then a Service Bulletin about the original studs not having enough thread to fully secure the Gear Pump. These studs DO have longer threads to ensure the Gear Pump can be secured properly. They are SOLD EACH, so you will need to order (3) of them. You can see in the picture the nut ran out of thread before it was properly torqued. You can also see the longer thread on these new Pump Mounting Studs. Click on Related tab for new Nylock Nuts. Much easier to install the Gear Pump with studs vs. bolts. What I have found in the shop is often the short studs will cause the pump to suck in air, particularly when it is below 0. There will be foaming. The unit may leak fluid in between the Sump Bsse and the PA Block. You can easily remove one stud without upsetting anything, if you want to check yours. IF the nut is bottomed out (ran out of threads) like in the picture then you need to replace yours.