Surgical implants are configured for placement posteriorly to a spinal canal between vertebral bodies to distract the spine and enlarge the spinal canal. The micro-speaker assemblies include a micro-speaker positioned in a housing. At least one of the blades may have a physical nonuniformity. The electrolyte layer covers the isolation layer, and provides a source of ions that place the reference cell in ionic andor electrical contact with a fluid sample. Preferably, the wick is configured such that ink flows to the outlet port irrespective of an orientation of the ink jet cartridge. 5\u2266h\u22664, wherein r1 represents the minimum radius of the can body, r represents the maximum radius of the can body, h represents the height of the can body, and R represents the radius of the laminated steel sheet having a circular shape before shaping whose weight is the same as that of the can body.