Fastening devices are described. In one example, the fastening devices can be used for a landing string buoyancy solution. The landing string hardware includes a stop collar to be fitted and secured around a drill pipe and stop collar hardware to secure the stop collar together around the drill pipe. The stop collar can be secured at one end of a number of buoyancy modules placed along a longitudinal length of the drill pipe to hold them into place along the drill pipe. The stop collar can be formed from long fiber thermoplastic using extrusion-compression molding. The stop collar hardware includes a bolt having an external thread formed from long fiber thermoplastic and a nut having an internal thread formed from long fiber thermoplastic. Both the stop collar and the stop collar hardware are tested for suitability for the application of holding the buoyancy modules in place under operating conditions.