for (EntityPlayer ent : mc.world.playerEntities) {
double center = (0.6000000238418579 + value) / 2.0;
ent.setEntityBoundingBox(new AxisAlignedBB(ent.posX - center, ent.posY, ent.posZ - center, ent.posX + center, ent.posY + ent.height, ent.posZ + center));
}