FrIM stands for Freestyle IM. In FrIM, you do the regular IM order, but replace butterfly with freestyle. It's meant to be a less tiring alternate to regular IM, so you can train for longer, or focus on the backstroke/breaststroke parts of the IM. It looks like this:
- Freestyle
- Backstroke
- Breaststroke
- Freestyle
So a 100 FrIM would be:
- 25m Freestyle
- 25m Backstroke
- 25m Breaststroke
- 25m Freestyle