A tech pack is a conversation between design intent and factory reality. It's where vague ideas become manufactured objects. The difference between a good spec and an expensive mistake is a tech pack that controls the outcome versus one that leaves the factory guessing.
What a good tech pack contains
Dimensions come first as tolerances, not wishful thinking. A pocket depth of 85mm plus 2mm minus 3mm tells the factory what variation you accept. Without that range, you get inconsistency across runs. Same logic applies to every measurement: strap width, bag depth, panel heights, stitch placement. The tolerance is the contract.
Materials live in construction specs, not feeling descriptions. "Soft nylon" is not a spec. "70D Cordura by denier, 1.1mm thickness, calendered finish, colour Olive 308" is a spec. It means replacement batches are actually the same. Fabric descriptions should include weight (gsm), weave construction, base fibre content, and finish. If colour matters, include pantone or lab values.
Seam engineering gets written down. Stitch count per inch. Seam type (flat fell, bound, fake flat fell). Thread tension and type. Whether seams are reinforced at stress points. Seam allowances. Most brands don't specify this then express surprise when seams fail or puckering appears. The factory defaults to what's fastest, not what's right for the material.
Component specifications include part numbers and datasheets. Not "a good quality slider." YKK #5 coil slider, #20 puller, brass stop box. Not "metal D-ring." 25mm welded steel D-ring, minimum 500kg break strength, nickel plated. Not "threads." Gutermann Mara 50 polyester, colour to match XYZ. Every hardware item on the bill of materials needs traceability.
What a bad tech pack looks like
Sketches without specs are aspirational drawings, not manufacturing instructions. A side-elevation sketch showing strap placement looks clear to the designer. To a pattern maker reading in Mandarin or Vietnamese, it's ambiguous. Is the strap 5mm from the edge or centred? Does it stay parallel or angle inward? The sketch needs dimensions and construction notes.
Materials described by feel ("supple canvas," "buttery leather," "crisp") are subjective and unverifiable. Two different canvas suppliers have completely different "suppleness." The fabric needs quantified characteristics: breaking strength, elongation percentage, weight, finish type. This is what leather house buyers actually work from.
Missing tolerances mean missing control. "Cut to size" leaves too much room for variation. "Pocket opening 120mm plus 5mm minus 2mm" is clear. "Webbing stitched 10mm from edge" becomes 8mm on one side, 12mm on the other. "Webbing stitched 10mm from edge, plus 1mm minus 1mm" removes the guesswork.
Incomplete hardware specs create substitution risk. The factory specifies nothing about thread, finds YKK on backorder, and substitutes with whatever coil zip is in stock. It might be fine. It might not. The tech pack should lock down exactly what gets used and what acceptable equivalents are if primary supply fails.
The cost of vagueness
A good tech pack takes longer to produce. The return shows up in consistency, reduced rework, faster production cycles, and fewer customer complaints about quality variation. A bad tech pack saves design time but costs time and money in the factory, in QC, and eventually in customer satisfaction.
The factory works from what you give it. Sketches and feelings give you inconsistency. Specs and numbers give you the bag you designed.
We've watched brands rescue failing production by stopping everything and completing the tech pack properly. It slowed the schedule by a week. It fixed the quality problem permanently. That's the value of specification discipline.
