They come in two sizes 1/4" and 3/8". On our unit they used the 1/4" for the stove on the outside kitchen and 3/8" on the rear for the bumper mounted grill. I can only guess they thought the grill needed higher flow rate for the btu's. You did not mention the brand of your grill. Many brands sell conversion kits, google the brand and regulator removal you may find what you need. There have been many posts on this forum to try searching the forum as well.
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel