Describe the problem, not just the part
Tell us when the fault occurs: during opening, after rain, in cold weather or all the time. Send a full-window photo, a close-up of the fault and any manufacturer label you can safely reach. Do not force a jammed sash or handle. Parts compatibility depends on the original system and condition.
Glass: identify what needs replacing
Cracked glass and moisture trapped between panes are different problems. A sealed insulating-glass unit may be replaceable while retaining a sound frame; surface condensation can have other causes and should be diagnosed first. Glass thickness, coatings, spacer, grids and safety-glass requirements must match the application. Do not handle broken glass yourself.
When a larger replacement makes sense
Rot, distorted frames, repeated water entry or unavailable parts can change the options. A repair should address the diagnosed cause rather than hide symptoms with extra sealant. Ask which components stay, which are renewed and how operation and water management will be checked. Availability and repair scope are confirmed after assessment.