Sharp edged t-posts can injure horses and livestock. Our Heavy Duty T-Post Topper Insulator can give you peace of mind as they protect animals from sharp edges.. Safe and flexible – add a single electric wire/tape/braid to the top of existing steel posts using this protective cap or attach wire/braid to the top. This top accommodates 3/8″ wire. The front accommodates 1 1/2″ tape and 3/8″ wire.