Fitting on the Razer Kraken Pro headset is very easy, pull the material over the surface of the speaker, and secure it by tension.
To fit the earbuds to the Sennheiser HD215, HD225 use the plastic ring from the old earbuds and install the new ones as shown in the picture below.

2 reviews for PadForce® Earpads Cushion for Razer Kraken Pro headphones, Over-Ear