The selection of spacer type depends on the following dimensions:
| Carrier Pipe O.D. | Recommended Solution | |
| Small | Up to 177 mm or 7 inches | S/T or C/D/I |
| Up to 304 mm or 12 inches | A/B | |
| Medium | Up to 508 mm or 20 inches | F/G |
| Up to 838 mm or 33 inches | M/N or P/Q | |
| Large | Up to 1270 mm or 50 inches | L |
| Up to 3810 mm or 150 inches | E/H |