"GREAT LAKES"-{ALR23}-"SWEETWATER" - 9" Replacement Air Diffusers - by Bubblemac Industries, Inc. manufacturers of"The Forever Bubble Stone" 100% Glass-Bonded Silica Each Bubblemac Air Diffuser measures 1.5" x 1.5" x 9" with a 1/2" MPT Fitting That Will Thread Directly Into The Great Lakes Underlayment. {Suggested CFM = 1.5 or 40-45 lpm} Made In The USA With A Two-Year Warranty. ALL Bubblemac Products Boast A "NO QUESTIONS ASKED" Return Policy. If You Do Not Agree That Our Aeration Products Outperform The Competetions Diffusers, Simply Return Them For A Full Refund! -- "Made Locally / Used Globally" -- Diffuser Specs: Maximum Pore Size 140 Microns, Nominal Partical Retention 50 Microns, Flexural Strength 2500 PSI, Bubble Size 1-3 MM, SERVICE LIFE UNLIMITED When Used In pH 8.0 Or Less. These Air Diffusers Should Not Need To Be Cleaned For One Full Year. When Cleaning Is Necessary, Simply Bath In A Diluted Solution Of Muriatic Acid {mild swimming pool acid}, Rinse Well and This Will restore The Diffuser To "Like New Performance" Bubblemac Air Diffusers are Time-Tested and Proven To Be The Most Effective, Most Economical Method Of Increasing Aeration Available On The Market Today! 3.5 Million Units Manufactured And Distributed To Fish Farms, Hatcheries, College Labs, and Wastewater Treatment Facilities Over The Past 16+ Years. Buy The Best, Buy Direct From The Manufacturer. BEWARE OF IMITATIONS!!! Bubblemac diffusers are the original 2000F glass-bonded silica air diffusers introduced by Bob Heideman founder of Aquatic Eco-System in 1978. You may come across other diffusers that copy our sizes, descriptions and even our photos.