If you mean lower build quality plastic cover on U-Lock, from security point is not important. The most important thing is, what lies under the protective plastic or hard rubber cover.If you completely destroy the protective plastic housing, U-lock is still there to be precise one-piece U-Lock body from hardened steel.On this photo is OnGuard Pitbull, so from security point no plastic cover= absolutely no problem.;)
If you mean lower build quality plastic cover on U-Lock, from security point is not important. The most important thing is, what lies under the protective plastic or hard rubber cover.If you completely destroy the protective plastic housing, U-lock is still there to be precise one-piece U-Lock body from hardened steel.On this photo is OnGuard Pitbull, so from security point no plastic cover= absolutely no problem.;)
OnGuard Bulldog/Pitbull/Brute/old models black-gray plastic cover, today models black-yellow color combination
http://www.bikeradar.com/gear/category/accessories/locks/product/review-onguard-bulldog-dt-39853/
http://gizmodo.com/5922074/the-best-bike-lock
http://road.cc/content/review/13674-onguard-brute-u-lock