Remington 870 warhammer heatshield/rail?

i have a remington 870 and was considering purchasing the warhammer,so i could place a rear and front sight on it and possibly a scope.i was wondering if this rail system is worth the 100+dollars.and if it would easily mount onto a short barrel such as my 18inch,as i know the rail is considerbly long.a few pros and cons on this subject would help.