What to specify what to ask a display supplier and how to avoid the errors that make a POP order arrive wrong.
Almost every display problem traces back to a missing product dimension. Before anything else, record the height width and depth of the item the display has to hold, and the number of facings you need. A display quoted without those numbers is a guess.
Counter depth, clear height above the counter and shelf height inside a showcase all constrain what can physically be used. Measure them at a real store rather than reading them off a plan.

Order the fixtures that stay separately from the items that change. Fixtures are an acrylic decision. Campaign structures counter cards and banners are print decisions on a shorter cycle.
Where a material or a size is not recorded, ask for it in writing rather than assuming it from a photograph. On the ONELINK POP product pages sizes and materials are shown for the models where they are recorded, and where they are not the page says so.
The single cheapest quality improvement in a POP programme is ordering the display the counter card the bag and the banner from one factory. Colour matching across suppliers is the problem that eats the most time and the most reprints.
Product dimensions facings per display quantity material preference and your target date.
For anything that has to hold a product, yes. A sample is the only way to confirm the real item fits.
Because colour matching between separate print suppliers is where most POP programmes lose time and money.
Send your product dimensions and counter space and the team will point you at the range that fits.