Start with the groove, not with the seal
Most profiles that fail to fit do so because they were drawn from the outside in. The groove depth, the gap the seal has to bridge and the compression available are fixed by the hardware; the seal has to adapt to them. Send the groove drawing and the assembled stack-up rather than a seal sketch alone, and the first tool will usually be the only one.
Put material where the compression happens
In an extruded profile the mass does not have to be even. A hollow bulb compresses on very little force while a solid heel holds the section in the groove, and a lip can be made thin enough to flex without adding closing force anywhere else. That is the advantage over a catalogue section: material goes where it does work, which also keeps weight and compound cost down.
Durometer is a range, not a number
Silicone for sealing is typically specified between 30 and 80 Shore A, and asking for a single value without a tolerance is asking for an argument later. A sensible spec is a mid-point with a plus or minus five point band, and the mid-point should follow the job - softer where the flange is uneven or the closing force is low, firmer where the seal has to resist being pushed out of a shallow groove.
Pick a tolerance standard before inventing one
ISO 3302-1 defines dimensional tolerance classes for extruded rubber products, and most suppliers quote to the middle class by default. Naming the standard and the class on the drawing removes a whole round of questions. Holding a tighter class than the assembly needs is possible, but it costs tooling attention and scrap, so tighten the tolerance only on the dimensions that actually seal.
Solid, sponge or foam - choose by closing force
A solid section gives the best recovery and the longest life, but needs real force to compress. A sponge or foam section closes on a light latch and follows an uneven surface, which matters on long doors, enclosures with flatness variation, and any assembly where the hardware cannot take the load. Where both are needed a co-extrusion can put a dense foot in the retainer and a soft sealing bulb above it.
The two ends decide whether the loop closes
An extruded length has no memory of being a ring, and the joint is the part that leaks when it is left to whoever assembles it. Decide early whether the profile is cut to length and bonded on site, vulcanised into a continuous ring, or mitred and glued at the corners, and say so on the drawing - each route changes the cut length allowance.
What to send when you ask for a quote
A DXF or PDF cross-section with dimensions; groove depth and available compression; service temperature range; what it will be exposed to, including any oil, cleaning agent or UV; target durometer with a band; colour if it is not going to be black; and the joining method. Material certification requirements belong in the same message, because they can change which compound is available. Volume and destination port help us quote sensibly.
Profiles for this application
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Working on something like this?
Send the drawing, cross-section, operating temperature and what the seal has to resist. We will tell you whether a stock profile fits or the part needs extruding, and quote both.