The 21 gallon water tank measures 39" x 16" x 8" (not including fittings) and the This 30 gallon water tank measures 34" x 18" x 12" (not including fittings) All tanks come with (1) 1.25" water fill inlet and (3) 3/8" NPT connections. Non-Pressurized Tank - The tank must be vented One piece seamless construction - No Seams to burst These rotational molded fresh water tanks are made from a high quality durable polyethylene material. Stain, corrosion and rust resistant features make them ideal for replacement or OEM installation on RVs, horse trailers or marine products. PLEASE MEASURE YOUR INSTALLATION AREA PRIOR TO PURCHASING. We offer a wide selection of sizes and varieties of tanks to service your RV, food truck, or concession trailer. All our tanks are BPA free and have a seamless construction to prevent blow-outs and leakage. Our tanks are offered in a combination package of fresh water and gray water as you need both for your concessions or trailer to function properly. Our tanks offer multiple ports for easy access to your specific hook-ups.