- To assist deep-hole measurement
- Can be used for bore gages 2322 and 2122
| Code | Appicable bore gages | A | D | Remark |
| 7351-EX11 | 475 | 13 | one piece | |
| 7351-EX12 |
35-60mm, 50-100mm, 50-160mm, 100-160mm |
980 | 13 | one piece |
| 7351-EX13 | 1480 | 14.5 | consist of two pieces | |
| 7351-EX14 | 1980 | 14.5 | consist of two pieces | |
| 7351-EX21 | 480 | 14.5 | one piece | |
| 7351-EX22 |
160-250mm, 250-450mm |
980 | 14.5 | one piece |
| 7351-EX23 | 1480 | 14.5 | consist of two pieces | |
| 7351-EX24 | 1980 | 14.5 | consist of two pieces |