Boveda MB49HA-40-20P Two-Way High Absorption Humidity Control, 20-pack 40g, maintains 49% RH - 20 pcs

Boveda MB49HA-40-20P is a value 20-pack of Boveda two-way humidity control packs (Size 40, 49% RH) in the special High Absorbency (HA) version.

Designed specifically for wooden musical instruments—especially acoustic guitars, bass guitars, cellos and bassoons—stored in areas with consistently high ambient humidity above 50–60%. The Boveda High Absorption (HA) packs stabilise the humidity inside the instrument case to help protect wood, glue joints and playability in damp climates.

Key features:

• Target humidity: Maintains relative humidity in the instrument case within the optimal range of 45% to 55% (49% RH packs).
• High Absorbency (HA) version: Absorbs up to 3× more excess moisture than standard 49% Boveda packs—ideal for rainy climates, coastal areas, or humid summer months where wood warping and mould can become a risk.
• Size 40: Each pack weighs 40 g and measures approx. 13.3 × 8.9 cm (5.25" × 3.5").
• Pack size (20-Pack): The 20P code indicates a pack of 20 units, typically supplied in a resealable, reusable bag to prevent the packs drying out/absorbing moisture before use.

Who it’s for / best use: Ideal for players and owners of acoustic and other wooden instruments who live or tour in humid regions and want stable case humidity without refilling water-based humidifiers. Suitable for any genre or playing style—from fingerstyle and classical to strumming, flatpicking and studio work—where consistent instrument condition and tuning stability matter.

Use & lifespan: Place the packs in dedicated fabric holders (Boveda Fabric Holders) inside the instrument case. Typical lifespan is 2 to 6 months, depending on conditions and how well the case seals. Replace when the pack becomes completely rigid or, conversely, swells to its maximum from absorbed water.

Important: The manufacturer strongly recommends not combining these packs in the same case with other humidification systems (e.g. sponge humidifiers) or with other Boveda percentage versions, as they will work against each other.