the 19 shed and 20 shed post insulator data is put in the web today.the 21 shed is customized product ,often the post insulator used for the station ,but this 21 shed product it can used for equipment.it is our south africa cleint to need.if you have some insulator to need and you can't find the data in our web ,please mail to us,we can supply theSuitable products to you.our mail is zonri@188.com and zhorui@188.com,nancy and jame will reply you soon.