Part Description = PISTON. Model Count = 2. DR500X 1981 500 DR500 DUAL PURPOSE. SP500X 1981 500 SP500 DUAL SPORT. Hi/AK/PR/APO AP may be higher. Customer service is our #1 priority. We strive to be the best at what we do. All Sales are Final unless item is misrepresented. Please contact me prior to leaving feedback if we did not provide “5 Star Service”. The part number alone gives you all the information if this part is correct for your bike! If you are not sure please message me. Unless item is misrepresented.