Why a large plastic projection on the W500 DVD/CD Ultrabay?

[bighank]

My W500 DVD/CD Ultrabay has a large plastic projection on the side which contacts the pins ie. the rearmost or back side of the Ultrabay. I also have a SATA 2 disk Ultrabay which had no such projection. My Ultrabays on my T61 and T61P have no such projections either (both DVD/CD and SATA 2 disk carriers).
What is the purpose of this projection. If it breaks off will the DVD/CD Ultrabay still functiuon correctly?

[richk]

Aftermarket units usually don't have the projection. The purpose is to keep you from putting a W500 ultrabay adapter into an earlier model. The SATA connector can be damaged