A device for joining two members together such as concrete segments (1, 2) for a tunnel lining ring includes a first sleeve (3) for fitting in one of the members to open at a surface thereof and a second sleeve (7) for fitting in the other member. A connecting pin (11) with external ribbing fits in both sleeves, which have internal ribbing, the ribbing of the connecting pin and/or the ribbing of at least one of said sleeves being of resilient material and extending in a substantially parallel direction at an inclined angle to a longitudinal axis of the connecting pin when it is, in use, inserted in the sleeves. The bore of one sleeve is of greater cross-sectional area in one dimension than the bore in the other sleeve, in which other bore the connecting pin can engage as a tight fit, whilst being able to engage in the firstmentioned bore and traverse it in said one dimension.