Prep M is a primer that is required when creating an adhesive bond for solid PVC, using Bostik High Tack adhesive. Bostik primer Prep M is an adhesive primer that is strongly recommended when fastening solid PVC using Bostik High Tack or Seal’n’bond adhesive. Pre-treating the solid PVC is necessary for ensuring a solid and strong adhesive bond. Prep M comes in a 500 ml container.