Hi Koh, I'm pleased to assist you. Good question. The valve stem seals may look the same, but there are often subtle differences in their design or material composition that make them specific to either the intake or exhaust valves. 1) Look for markings on the seals. Some valve stem seals are marked with a letter or number to indicate whether they are for the intake or exhaust valves. 2) Refer to the manufacturer's instructions. The manufacturer of the valve stem seals should provide instructions on how to install them correctly. These instructions should specify which seal goes on which valve. 3) Compare the old seals to the new seals. If you are replacing old valve stem seals, you can compare them to the new seals to see if there are any differences in their design or material composition. In the case of the Apex AVS8055, the seals are numbered differently. This is because the seals are designed for different applications. The seals with the lower numbers are for the intake valves, and the seals with the higher numbers are for the exhaust valves (AVS8055-1: Intake valve seal, AVS8055-2: Intake valve seal, AVS8055-3: Exhaust valve seal, AVS8055-4: Exhaust valve seal, AVS8055-5: Exhaust valve seal). Consult the engine's service manual or a reliable source to determine which valves are intake and which are exhaust. You can use the link below to directly place your order. Take advantage of our low price and limited stocks. I hope this helps, and enjoy shopping! https://www.carparts.com/valve-stem-seal/apex/apxavs8055?can=CPGG4850_CSQA_20231109