Separate product choices
A fixed window, opening window and sliding door require different components. Glazing, colours, hardware and accessories also influence the proposal. Request a breakdown by element so you can discuss possible alternatives without losing sight of the full specification.
Include the work
Measuring, removal, transport, installation and finishing may be included differently. Check disposal, access and repairs to surrounding surfaces as well. A lower total only becomes meaningful when you understand whether the scope of work is equivalent.
Compare readable quotations
Place proposals side by side using the same dimensions and specifications. Highlight missing items and ask for assumptions to be explained. Record options and possible additional costs in advance, including how changes after final measuring will be handled.