the 112-75 piston fits the AH and AK one cylinder gasoline engine plants. FYI - the 112-75 piston fits the AH and AK one cylinder gasoline engine plants, and even though the model letters run sequentially it does not fit the AJ model which has the 112-74 piston which is 2 3/4" dia, NEW OLD STOCK PISTON 112-0171-10 same as 112-0075-10 ONAN 2-1/2" DIAMETER .010 OVERSIZED COMES WITH PIN AND 112-0013 RING LOCKS I have several of these pistons available. I USUALLY HAVE MORE STOCK OF ALL MY ITEMS AND CAN SAVE YOU MONEY IF YOU ARE INTERESTED IN LARGER QUANTITY PURCHASES. I AM ALSO GLAD TO SELL YOU A SPARE IF THAT IS ALL YOU NEED. If you have further information regarding this or another item I have for sale, please feel free to let me know so that I may post it here for buyers who may not have such information. Please look at my other items in my STORE and add me to your favorites list. click on SEE OTHER CATEGORIES NOS means new old stock. These are items that are still in new and unused condition that have been on the shelf or in storage for a number of years. Most of my items are in the original factory boxes or cases. Some of these boxes show a good bit of wear and tear from storage time and handling. I try to add to my store listings all the time. Please keep in touch. Most items are sold "AS IS" with a "no return policy" unless stated otherwise in the body of the ad. Please know what you are buying and ask questions if you don't. I will answer all emails to the best of my ability. If you are not satisfied with your purchase please contact me immediately. I am not an expert concerning much of what I sell . Please send part numbers when inquiring about certain parts. Sincerely, Mike ... ** ask me for help to search 1000's of old, obsolete and discontinued Onan part numbers. Hi, FYI - the 112-75 piston fits the AH and AK one cylinder gasoline engine plants, and even though the model letters run sequentially it does not fit the AJ model which has the 112-74 piston which is 2 3/4" dia, Powered by Turbo Lister The free listing tool. List your items fast and easy and manage your active items. 11-3-2021