Abstract: A tennis ball including a spherical hollow elastomeric core having a specific gravity of less than 1 and a thickness of at least 4.5 mm, and a textile layer covering the spherical elastomeric hollow core. The spherical hollow core has an initial internal pressure of no greater than 5 psi. The tennis ball has a first tennis ball rebound height when measured at a first time when the tennis ball is unused and a second tennis ball rebound height measured after the tennis ball is exposed to atmospheric pressure for four months following the first time and is unused. The second tennis ball rebound height being at least 96% of the first tennis ball rebound height.

Abstract: A dental apparatus for perforating the cortical plate of human maxillary and mandibular bones comprises a solid metal needle moulded into a plastics shank, the shank being formed with means for cooperation with a dental contra-angle or straight handpiece into which the shank may be inserted. The shank has a collar at its front end, and a hollow protective cap is removably fitted over the exposed needle and engages the collar.

Abstract: A dental apparatus for perforating the cortical plate of human maxillary and mandibular bones comprises a solid metal needle moulded into a plastic shank, the shank being formed with means for cooperation with a dental contra-angle or straight handpiece into which the shank may be inserted. The shank has a collar at its front end, and a hollow protective cap is removably fitted over the exposed needle and engages the collar.