This solder wire is 3.2mm diameter and is 60/40 grade (60% tin and 40% lead) which we find gives the best finish. It stays liquid long enough to create a nice smooth finish. We can get 50/50 grade if required. This has a higher melting temperature which does make it stronger but also makes it set quicker and therefore harder to get a nice finish.
Note that this solder has no flux core so you need to brush with either liquid or paste flux before applying.