what gauge extension cord for generator

{"cid":"91181013","title":"Universal Generator Auto Retractable Extension Cord Reel , Flexible Power Cable","imgUrl":"https:\/\/img.chinax.com\/nimg\/83\/5d\/93602c5aae8a60a81ac321ba411d-200x200-1.jpg","attrs":{"Price":"Negoation","Brand Name":"SFC","Model Number":"SFC-GFCI-02","Minimum Order Quantity":"100PCS","Delivery Time":"25Days","Certification":"ETL","Place of Origin":"Jiaxing,China","Payment Terms":"T\/T, LC","Supply Ability":"10000PCS Per Month","Packaging Details":"every one into plastrics poke and box. 5pcs into paper CTN.","Material":"ABS , PA66 UL94V0","Rating":"20a,125vac, 30A 125VAC","outlet quantity":"20A 125VAC GFCI duplex outlets","Color":"Black|Yellow","Power Cord Length":"15 ft","Cord":"UL approved 10AWG"}}

{"cid":"91222776","title":"ETL Listed 3 Prong 30 Amp Generator Cord 25 Feet Heavy Duty NEMA L5-30P\/L5-30R 10 Gauge 125V SJTW Lock Generator Extension Cord","imgUrl":"https:\/\/img.chinax.com\/nimg\/e7\/0c\/b04cbba538ae172ecbf92bf2fc48-200x200-1.jpg","attrs":{"Price":"CN\u00a5556.53\/pieces 1000-2999 pieces","Brand Name":"Sheng An","Model Number":"SH-L5-30","Minimum Order Quantity":"1000 pieces","Place of Origin":"Zhejiang, China","Type":"AC Power Cord, Power Cord","Application":"Home Appliance","Male End Type":"NEMA L5-30P","Female End Type":"NEMA L5-30R","Plug standard":"US","AC outlets quantity":"1 Outlets","USB Type-C ports":"0","Length":"6FT\/8FT\/10FT\/12FT\/25\/40FT","Color":"Blue\/Customization","Package":"Color Sleeve +Carton Box","Certification":"ETL","Conductor":"Bared stranded cooper","Jacket Material":"PVC","Cable":"3X8\/10\/12\/14\/16AWG","Rated Voltage":"125V","Rated Current":"15A"}}