The TR1 is best for small things that are thin at the top, like 6714 20mm stars and 6722 16mm crescent moons.
TR2 is great for Swarovski's 8558 20mm balls, 8611 40mm pencil drops & pieces that are not too fat at the top.
TR5 is perfect for Swarovski's 8558 30mm, 8611 63mm and Asfour's 3855 30mm, 3856 63mm, etc.
TR6 is what you want to use for much larger pieces like 8558 or 3855 50mm and larger.
The above are just suggestions, what really matters is how wide the top of the crystal is. The best solution is to buy a few of each if you are not familiar with the crystals you are purchasing.