Acrylic Mirrors can be recommended. They are similar to glass in their reflective quality, they are easy to handle and have a soft surface.
Whilst the mirror will show scratches over time it will remain highly reflective and will not the horse’s teeth should biting be an issue.
We also use acrylic mirrors for our Wild Child System!
To minimise distortion we mount the mirror onto a UV stable PVC plastic board. Since stables can be humid or damp on occasion, the backing copes with water penetration and limits bending and bowing by guaranteeing a flat and level surface. Further, the PVC material has a degree of cushioning should the mirror be kicked and helps support the acrylic where it has to span the uprights on unlined walls.
To contain the possibility of unattached shards the mirror is both glued and mechanically fixed to the backing.
The mirrors have radius corners and come with predrilled holes and dome head stainless steel fixings. No potentially harmful glues are used in the manufacturing or fixing process.