A diffuser is another type of downstem for a bong. Contrary to a downstem, a diffuser resembles a test tube as its sealed on the end or pierced with many small holes or slits. These slits break up the smoke into smaller bubbles than a normal downstem.

Why the need for smaller bubbles? The smaller the bubbles, the greater the surface area of the smoke that contacts the water, thus filtering and cooling the smoke more efficiently. This makes the bong almost silent silent. Many glass companies sell diffusers to fit their bong: Roor, Phx, and Bluedot.
EHLE Reducing Diffuser – 29.2 to 18.8 (Flame Polish Logo)
This EHLE Reducing Diffuser will allow you to transform your 29.2 joint size bong into a 18.8 joint size. The male joint is 29.2, but the female joint is 18.8 to take 18.8 size bowls only.
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EHLE Diffuser 18.8
EHLE’s replacement parts are made with precision joints and EHLE are rightly proud of them. Technically speaking, these 18.8 joint size EHLE puncture-hole diffusers leave nothing to be desired.
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G-Spot - Diffuser 18.8
In contrast to ordinary down-tubes, the end of a G-Spot - Diffuser's tube is sealed but pierced with many small holes. This allows for distribution of the smoke as it exits the end of the tube in many small bubbles.
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Molino Glass - Diffuser/Reducer
Molino Glass always put a lot of care and quality into their craft, and that is evident again in these Diffuser/Reducers. Ideal as a spare part for such a bong
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Black Leaf Acrylic Self-Lighting Bong - Clear
Black Leaf Acrylic Self-Lighting Bongs have a built-in lighting device which promotes comfortable and easy usage.
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Festival Glass Bong - Blue & Yellow Classic Pipa
Festival Glass bongs feature timeless designs and exceptional high quality glass. They have a very solid feel and a premium finish. The glass thickness of the Festival Glass ranges from 7mm to 10mm with the base especially thick, heavy and reliable.
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