Stack Height Flexibility — One Plug, Four Gaps
A single 5177986-6 plug mates with the corresponding Free Height receptacle at four different mated stacking heights: 5mm, 9mm, 13mm, or 17mm. That means one BOM line for the plug covers multiple board-spacing variants in a product family — the same connector works whether the mezzanine gap is tight (5 mm) or generous (17 mm). The actual stack height is determined by the receptacle height, not the plug; the plug's height above board is fixed at 0.191" (4.85mm). For the board layout engineer, this simplifies the footprint: one plug land pattern, one reel on the line, and the receptacle height is the only variable.
The closest functional peer in the Free Height family is the 1-120532-2, a 84-position plug on a wider 0.039" (1.00mm) pitch. The 5177986-6 packs 140 positions into the same two-row format at 0.80 mm pitch — 56 more circuits in a denser footprint. The 1-120532-2 carries a thicker 50.0µin (1.27µm) gold finish, compared to the 8.00µin flash on the 5177986-6, making the 1-120532-2 the better choice for applications requiring higher mating cycle counts or more corrosive environments. The 1-120532-2 also has a pick-and-place feature and ships in box rather than tape and reel. For a high-density, moderate-cycle mezzanine interconnect, the 5177986-6 is the denser, more cost-effective option; for ruggedized or high-cycle duty, the 1-120532-2 with its heavier gold is the safer call.