My title is office administrator, not materials engineer, but I'm the person who places the purchase orders when operations and finance hand me a vague request. I manage purchasing for a 160-person engineering services company—roughly $90,000 a year across about a dozen vendors. Once I started thinking in total cost of ownership, not the lowest quote, most of my buying decisions got less embarrassing.

This checklist is for purchases like Momentive silicone rubber, custom rubber wristbands, silicone foam tubing, and even insulation board. It won't replace a proper engineering drawing, but it will keep you from paying for the same material twice.

When to Use This Checklist

Use it when a purchase request shows a brand name but no specification. Use it when someone says 'just order the usual tubing' and you're not sure what 'usual' means. Use it before you make a decision based on the lowest number on a quote.

Step 1: Turn a Brand Name Into a Spec

'Momentive silicone rubber' is not enough information. Momentive silicones makes dozens of rubber grades. Some are liquid silicone rubber, some are high-consistency rubber, and they come in different hardness levels, tear strengths, and cure systems.

Before I send out a request for quote, I ask for three things:

I once spent a week comparing quotes for 'Momentive silicone rubber' and picked a supplier 12% cheaper. The material arrived with the right brand name but the wrong durometer. We almost used it anyway. Good thing we didn't, because the parts failed compression testing. The testing cost more than the money we saved.

Step 2: Ask What the Rubber Wristband Is For

Rubber wristbands look easy. Vendors sell them by the thousands, and they're cheap enough to feel like a low-risk order. That's exactly where the hidden costs live.

A 7.5-inch promotional wristband is not the same as a thicker medical ID wristband, even if both are made from silicone rubber. The promo wristband has to hold a printed logo; the medical wristband has to survive being pulled and snapped daily. If you choose the lowest-cost option without knowing which one you need, you'll get a nice bracelet with the wrong print quality or the wrong strength.

If the wristband carries your company logo, send a Pantone PMS number instead of a screenshot. According to Pantone Color Matching System guidance, a Delta E below 2 is the usual target for brand-critical colors. A Delta E above 4 is visibly off to most people. A vendor that doesn't match colors the first time will usually match them after an expensive reprint.

Step 3: Measure Silicone Foam Tubing Like It's Going to Be Inspected

Silicone foam tubing is another one of those 'how hard can it be?' purchases. It's not hard if you know the dimensions. The first time I ordered it, I asked for 'standard size.' The vendor said '3/8-inch inner diameter stock.' I said 'sure.' We both meant different things. They meant a tubing that fit their catalog; I assumed it would fit a 3/8-inch connector. It didn't seal.

Now I make any silicone foam tubing request include three measurements:

Also note the temperature range. Many people assume silicone foam handles high heat because the material family is good at high temperatures, but that's not automatically true for every foam grade. If you don't specify service temperature, the supplier will pick a default that's probably fine—but 'probably' is not a purchasing strategy.

If the supplier says the silicone foam tubing uses a Momentive silicones compound, ask for the exact product designation. The raw material name doesn't tell you the density or compression set of the finished tube. Those numbers are in the datasheet.

And if you can't get a drawing from the person who asked for it, take a picture with a ruler. That works better than a phone tag conversation full of 'standard' and 'regular.'

Step 4: Compare Fiberglass Insulation vs Foam Board on Total Cost

When I first compared fiberglass insulation vs foam board, I thought the decision was just the R-value and the price per square foot. It's not. Fiberglass is generally cheaper upfront and easier to cut in big open walls. Foam board gives you more R-value per inch and also works as a moisture barrier, but it costs more and can crack if it's over-tightened.

The real number is total cost, which includes material, waste, labor, and disposal. If the crew is working in tight spaces, foam board's rigid edges can save hours. If the project is a huge warehouse with clear walls, fiberglass will usually be the lower-TCO choice.

I also ask how much waste the quote includes. A low quote on fiberglass means nothing if the installer needs 20% extra, while the foam board quote might already account for odd shapes. Put both bids into the same format before comparing them.

Step 5: Verify Invoicing and Certifications Before You Say Yes

This is the step most people skip because it feels like an accounting problem, not a buying problem. It's a buying problem.

A few years ago, a supplier quoted $400 less than the incumbent. The product was fine. The invoice was not—handwritten receipt, no tax ID, no line items. Finance rejected the entire expense, and I had to explain why we did business with someone who couldn't issue a proper invoice.

In our 2024 vendor consolidation project, I cut a supplier whose material was okay. Their invoicing process wasn't. The material wasn't the problem; the process cost us far more than their lower price.

For silicone materials, ask for a material safety data sheet and, if the application touches food or the body, appropriate compliance documentation. A legitimate fabricator should be able to share product data. If the order involves printed products with environmental claims, review the FTC Green Guides before you approve the wording. The FTC is pretty clear that a claim like 'recyclable' has to be substantiated.

A product claimed as 'recyclable' should be recyclable in areas where at least 60% of consumers have access to recycling facilities. — FTC Green Guides

The Short Version

If you're in a hurry, here's the checklist:

After five years of managing these relationships, I'm more comfortable telling an engineer 'I need a drawing, not a description.' It's not glamorous work. But the small stuff—a wristband that fades, a tube with the wrong inner diameter, an insulation board that doesn't fit—eats hours. The total cost of those hours is almost always higher than whatever I saved on a quote.