My '95 C280's windshield was a PPG with the logo in the lower corner. The following two replacements were both PPG with the logo at the center bottom. Otherwise identical. My '01 C320's glass is all Pilkington. I went to the glass shop that does all my dealer's work and yes, the car must remain at least all day and preferably overnight until the cement sets up. This is an edict from MB dating back at least five years.