用於連接內螺紋鏡筒，並且可以調整相對距離
材質：鋁合金黑色陽極處理
.jpg)
| 型號 | 外螺紋(A) | 長度L(mm) |
| LT05C05 | SM05 | 12.7 |
| LT05C10 | SM05 | 25.4 |
| LT05C20 | SM05 | 50.8 |
| LT1C05 | SM1 | 12.7 |
| LT1C10 | SM1 | 25.4 |
| LT1C20 | SM1 | 50.8 |
| LT1C30 | SM1 | 76.2 |
| LT1C40 | SM1 | 101.6 |
| LT2C05 | SM2 | 12.7 |
| LT2C10 | SM2 | 25.4 |
| LT2C20 | SM2 | 50.8 |
| LT3C05 | SM3 | 12.7 |