drop down list

I am building a jbox that has multiple (16) conduit connections. I want those connections to be individual connections that can be either 1/2" radius or 3/8" radius but not consistently. So of the 16 connectors any number of them might be 1/2" radius where the others are 3/8". So I would really like this to be a drop down choice for each of the connectors... how do I do that?

so... I put this in the wrong forum...

In what forum should it have been placed?