The Dev XL Test Fixture Base is the long-format version of FixturFab's entry-level hinged fixture. It keeps everything that makes the Dev base useful for prototype work — the simple hinged closing motion, the swappable cartridge, the low cost of entry — and stretches the working area to suit elongated boards: strip PCBs, sensor bars, LED assemblies and panels that are far longer than they are wide.
Contact force and mechanism are unchanged from the Dev base, so the selection question is purely about board geometry: if the DUT fits the Dev footprint, buy the Dev; if it is too long for it, buy the XL. Both take the same style of cartridge, in G10 or MDF, so the probe field is a per-product item rather than a per-fixture one.
For a higher contact force, a parallel closing action or optional top-side contacting, look at the Dev Pro range instead.
