What Are Mic Foam Covers Actually Made Of?

To the untrained eye, all foam mic covers look identical. They're not. Three materially different types of foam dominate the market, and the difference between them affects sound, lifespan, print quality, and whether your cover survives an actual year of use.

Here's what's actually in the foam.

The three foam types you'll encounter

1. PU foam (Polyurethane) — the good stuff

Most premium custom mic covers are PU foam. Open-cell structure, slightly bouncy to the touch, recovers shape after compression.

Pros:

• Acoustically transparent (doesn't muffle the mic)
• Dye-sublimation prints embed cleanly into the surface
• Lasts 2-4 years with regular use
• Stays flexible across temperature swings
• Survives sweat/breath moisture without immediate breakdown

Cons:

• More expensive raw material (~3× PE)
• Degrades faster in UV (yellowing in 12-18 months of direct sunlight exposure)

This is what we use for all our standard covers, and what every reputable UK mic-cover shop uses.

2. PE foam (Polyethylene) — the budget stuff

The cheap foam used in Amazon-listed "fits all mics" covers. Closed-cell structure, stiffer, no spring back after squeezing.

Pros:

• Very cheap
• Doesn't absorb water (waterproof)

Cons:

• Acoustically dead in the upper midrange (3-6 kHz)
• Tears at seams within 5-20 wear cycles
• Print quality is poor — colour sits on the surface, abrades fast
• Stiffens in cold weather
• Brittle, breaks rather than flexes

If you've bought a £6 mic cover from Amazon and it tore within 6 months: it was PE foam.

3. Reticulated foam — the broadcast specialist

Reticulated foam is PU foam that's been chemically processed to remove the cell walls, leaving only the skeleton (the open lattice between cells). Looks more like a sponge structure under magnification.

Pros:

• Extremely acoustically transparent (less wind/plosive than even regular PU, but more open)
• Doesn't trap moisture or odour
• Used in high-end broadcast windscreens and pop filters

Cons:

• More expensive than standard PU
• Slightly more fragile to handling
• Not as good for printing — the open structure makes high-detail prints harder

You'll see reticulated foam in Rode WS-series windshields, Rycote products, and high-end broadcast mics. We use it in some specialist orders but standard PU is what most podcast/event customers need.

Why the difference matters

For a podcast setup recording at 10-25cm from the mouth:

• PU foam is right. Doesn't muffle, lasts years, prints cleanly. £20-30 retail.
• Reticulated foam is overkill but works. £40-60 retail.
• PE foam is wrong. Cheap, but it'll cost you a replacement within 6 months. £6-10 retail.

For a live-vocal SM58:

• PU foam with slightly denser cell structure. Handles sweat and handling. Same £20-30.
• Reticulated foam doesn't suit — too open, transmits moisture too freely.

For an outdoor mic in wind:

• Furry (wool/synthetic) over a PU foam core is the right combination.
• Plain PU foam alone doesn't kill wind effectively.

How to tell what you have

Squeeze the cover gently:

• Springs back fast = PU foam
• Stays compressed = PE foam (bad)
• Almost no resistance, feels mesh-like = reticulated PU foam

Smell it:

• Mostly odourless = PU
• Slightly plastic smell = PE
• Almost nothing = reticulated PU

Look at the surface up close:

• Visible bubble-like cells = closed-cell PE
• Visible open cells in a roughly even pattern = open-cell PU
• Visible sponge-like lattice with no cell walls = reticulated PU

What this means for buying decisions

When you're shopping for a custom mic cover, the foam type is usually not on the product page — most sellers don't disclose it. You can usually tell from the price.

Under £10 retail: almost certainly PE foam. Avoid.

£15-30 retail: typically PU foam. Standard for the UK market. Reasonable quality.

£30-50 retail: PU foam with custom printing. What we and most reputable UK makers charge.

£50+ retail: reticulated foam, or PU with very high-end printing/material. Specialist use.

We use standard medium-cell PU foam for our podcast covers and slightly denser PU foam for our live-vocal SM58 covers. Both at £20-30 retail depending on the mic.

Why this matters for print quality

The foam type also affects how well the print holds up:

• PU foam + dye sublimation = print embeds into the foam surface. Lasts years, doesn't crack.
• PU foam + screen print = ink sits on the surface. Lasts ~2 years before cracking around bend points.
• PE foam + any print = poor adherence. Cracks and flakes within 6-12 months.

If you've ever owned a custom cover where the print started peeling after a year, the underlying foam was probably PE. The print method matters, but the substrate matters more.

Bottom line

You're not buying foam. You're buying a year of professional-looking audio kit. PU foam at £20-30 gets you that. PE foam at £6 gets you a replacement order in six months.

Browse foam covers by mic model — we're transparent about what's inside ours.