Moeller Manually - vented Replacement Fuel Cap. SAVE BIG! Durable plastic Replacement Cap for your Moeller portable fuel tank. CSA / UL-Listed. Fits portable fuel tank models: Moeller 3-gallon Neptune Tank (model no. 004158); Moeller 6-gallon Neptune Tank (model no. 004921); Moeller Scepter 3.2-gallon Topside Tank with Gauge (model no. 003780); Moeller 6-gallon Portable Tank (model no. 003781); Handy boating accessories for less! Order Yours Today! Moeller Manually-vented Replacement Fuel Cap