Qualified products shall meet the following conditions: 

 1, the code name on the end face is consistent with the need 

 2, surface smooth, no defect, no deformation. 

 3, with skeleton rubber oil seal shape, the end face is round, placed on the glass plate, and glass surface should be fitted, no disturb phenomenon. 

 4, without skeleton oil seal edge should be correct, the end surface is smooth, with the hand to make it deformed, let go, can restore to the original shape. 

 5, the shape and thickness of the blade should be the same on the whole circumference. When the matching kit is installed, the edge of the blade should be tightly fitted on the matching neck. 

 6, with spring rubber oil seal, the spring should be no rust, no deformation, and can be firmly stuck in the spring slot. Take 50*72*12 rubber oil seal as an example. Make the oil seal fall freely from the height of 1m. If the spring falls off 5 times each time, no more than 1 times, then the spring and the oil seal can be well coordinated. 

 7, dealers buy in bulk rubber seals, can take samples of oil immersion test, measuring the rate of change of mass. For example, the oil seal with 25 transformer oil (70 + 5 degrees) 24h immersion temperature, the quality of the change rate should be between 3%-5%.