If you keep adjusting your underwear during a workout, start by naming the part you move. A waistband, a leg opening, and fabric at the front are separate fitting questions. Choosing the lowest listed weight will not necessarily answer any of them.
What coverage are you looking for?
GEARXPro Performance Second Skin is a brief, not a long-leg base layer. That matters before you compare fabric technologies. The verified product information does not establish inner-thigh coverage, so do not choose it on the assumption that it covers that area.
For someone who prefers a brief under training shorts, the relevant details are its shape, leg openings, and seam construction.
Read the edges as closely as the fabric
Second Skin uses low-profile bonded seams, raw-cut edges, and a three-dimensional front. Its stated fabric composition is 57% polyamide and 43% elastane, with stretch in four directions.
Compare those features with the underwear you already wear. Where is its seam positioned? Does its leg opening fold under your shorts? The reason to consider Second Skin is its documented construction, not an assumption that a technology name guarantees friction-free wear.
Use the product's own measuring point
The size guide asks for a circumference measurement six centimeters, about 2.4 inches, below the navel. Use that location rather than transferring a size from another brand. If your measurement sits on a boundary in the chart, ask for model-specific sizing advice.
During a fitting, raise your knee and return to standing. Observe whether the waistband and leg openings stay comfortable or need repeated adjustment. This is a fit check, not a medical test.
Open the Second Skin product guide with a clear question about coverage or seams. That gives you a more useful starting point than choosing by weight alone.